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NOTES 



ON 



THE TESTING AND USE 



OF 



Hydraulic Cement 



BY 



^ 



FRED P. SPALDING, 

Assistant Professor of Civil Engineering, 
Cornell University, Ithaca, N. Y. 



.^ 



01 COA^o 



'^^^ 



ITHACA, N. Y., 

ANDRUS & CHURCH, 

1893. 



'^OCT 27 1333. 



'ry 



OF WfcS 



r/ 







Copyright, 1893, 
By fre;d p. SPAI^DING, 



PREFACE. 



^TpHESE notes are designed for use as a text in a short 
■*- course of instruction, as well as to serve the purpose 
of a hand book in the laboratory. In the first three chap- 
ters, an attempt has been made to give a brief statement 
of the general properties and characteristics of hydraulic 
cement, and its behavior under the more common con- 
tingencies of use, with a discussion of the various tests 
which may be applied to it, including both the ordinary 
tests of practice and the more elaborate ones which have 
been proposed, or which are in use in the larger experi- 
mental laboratories. 

An effort has been made to give the best and most re- 
cent practice in cement testing, to point out the precau- 
tions necessary in making tests of quality, and to show 
the limitations within which the results of such tests may 
be considered as demonstrating the value of the material. 

In the fourth chapter is given a selected list of recent 
periodical literatvire relating to the subject, with topical 
references to the various articles, intended to facilitate 
the work of those desiring to more fully investigate any 
of the divisions of the subject, and especially to aid stu- 
dents engaged in original or independent research. 

References to authorities have not usually been given 
in the text, the list of literature in chapter IV seeming 
to render them unnecessary. To many of the papers 
there mentioned the author is indebted for information 
and suggestions. 

F. P. S. 

Ithaca, N. Y., 

Sept. 9, 1893. 



CONTENTS. 



CHAPTER I. 

NATURK AND PROPJeRTlES OF CEMENT 

Page. 

Art. r. Definition i 

2. Portland Cement 3 

3. Natural Cement 7 

4. Slag Cement 10 

5. Setting II 

6. Hardening • • 17 

7. Adhesion 24 

8. Soundness. Permanence of Volume .... 26 

CHAPTER II. 

CEMENT TP:STING. 

Art. 9. Object of Testing 29 

10. Weight and Specific Gravity 32 

11. Fineness . . . : 35 

12. Rate of Setting 38 

13. Tensile Strength 41 

14. Ordinary Tests for Soundness 57 

15. Accelerated Test for Soundness 60 

16. Chemical Analysis 68 

17. Compressive Tests 69 

18. Adhesive Tests 71 

19. Microscopic Examinations 72 

20. Abrasive Tests 73 

21. Air Slaking 74 



vi Contents. 

CHAPTER III. 

THK USE OP^ CEMKNT. 

Page. 

Art. 22. Sand for Mortar 76 

23. Water for Mortar ... 79 

24. Mixing Mortar 80 

25. Preparation of Concrete 82 

26. Mixtures of Lime and Cement 85 

27. Freezing of Mortar 86 

28. Permeability of Mortar ..... .... 90 

29. Expansion and Contraction of Mortar ... 92 

30. Retempering Mortar 94 

CHAPTER IV. 

I.ITKRATURK REIvATiNG TO CEMENT. 

Art. 31. List of Periodical Literature ........ 96 

32. Topical References to Papers 107 



THE TESTING AND USE 



— OF — 



HYDRAULIC CEMENT 



CHAPTER I. 

NATURK AND PROPKRTIKS OF CKMKNT. 



ART. I. DEFINITION. 

When a limestone, composed of nearly pure 
carbonate of lime, is burned, the resulting mass 
of quicklime possesses the property of breaking 
up, or slaking, upon being treated with a suffi- 
cient quantity of water* The slaking of the lime 
is due to its rapid hydration when in contact with 
water. The process of slaking is accompanied by 
a considerable increase in the volume of the mass 
of lime, which is reduced to powder, and by a 
rise in temperature. 

The powdered lime thus formed possesses the 
further property, when mixed to a paste with 
water and allowed to stand in air, of gradually 
hardening and firmly adhering to any surface 
with which it may be in contact. The hardening 
of nearly pure limes, which will occur only when 



2 Hydraulic Cement. 

in contact with air, is due to the formation of 
carbonate of lime by the absorption of carbonic 
acid from the air, together with a crystallizing of 
the hydrate from solution as the mortar dries out. 

If the lime have, mixed or in combination with 
it, more than about lo per cent, of impurities, its 
power of slaking is greatly lessened, if not en- 
tirely lost. If these impurities be of an inert 
description, the lime also loses to some extent its 
power of hardening, and is then known as poor 
or meagre lime. If the impurities in the lime 
be composed mainly of silica and alumina, they 
may, while lessening or destroying its property 
of slaking, impart to it the power to harden under 
water. The ability to harden in water is usually 
due to the formation of certain silicates and alu- 
minates of lime during the process of burning, 
which possess the property of solidifying when 
hydrated by contact with water. 

When the proportions of silica and alumina in 
the lime are such that the lime possesses the 
property of hardening in water, without having 
entirely lost that of slaking, the material is 
known as hydraulic lime. 

When the acquirement of hydraulic properties 
has been accompanied by an entire loss of the 
property of slaking, the product is an hydraulic 
cement. 

Hydraulic limes and cements may be made 



Portland Ceme7it. 3 

either by burning limestoiievS containing the 
proper proportions of hydraulic ingredients, in 
which case they are known as natural limes or 
cements, or by the admixture of material con- 
taining such ingredients to the limestone before 
burning, or to the lime afterward, when they are 
known as artificial limes or cements. 

The hydraulic properties of a lime or cement 
vary, within certain limits, according to the pro- 
portion of hydraulic ingredients contained by 
them, and the ratio of the weight of silica and 
alumina to that of the lime in the material is 
known as its hydraulic i7idex. For hydraulic 
limes, the hydraulic index may vary from about 
tW to yW- For cements it is usually between 
y\^o- and yy^Q, but is sometimes higher. 

Hydraulic limes are used in some parts of Eu- 
rope, but are not manufactured to any extent in 
this country. The American cement industry is, 
however, growing to very large proportions, and 
cement of all grades is extensively made, although 
large quantities of high grade foreign cements 
are still imported. 

ART. 2. PORTI.AND CEMENT. 

The term Portland Cement is commonly used 
to designate an hydraulic cement formed by burn- 
ing to the point of vitrifaction, a mixture of lime- 
stone and clay in proper proportions, and reduc- 



4 Hydraulic Cement, 

ing the resulting mass to powder by grinding. 
The production of a good Portland cement re- 
quires great care in manufacture ; the chemical 
composition must the accurate ; the mixture of 
the stone and clay must be thorough and uniform, 
and the burning must be complete. 

The action of the cement seems to depend upon 
the formation, during the burning, of the silicate 
and aluminate of lime, the other elements being 
considered in the light of impurities, although 
some of them may at times be of service in the 
cement. 

The hydraulic index of Portland Cement varies 
from about -^-^ to 3^, and its normal composi- 
tion is usually practically within the limits given 
below. 

Silica, 20 per cent. 

Alumina, . . 5 '* '* 

Iron Oxide, . . 2 " ** 

Lime, 58 '' '' 

Magnesia, ... 0.5 " '' 

Sulphuric Acid, 0.5 " ** 

If in mixing the ingredients too great a quan- 
tity of clay be used, the surplus will remain in 
the cement as inert material, causing a weaken- 
ing of its action. If the surplus of clay be con- 
siderable and the burning thorough, the material 
may be reduced to powder in the burning, produc- 
ing a cement of comparative little value. 



to 


25 per 


cent. 




8 








4 








65 








2 








I 







Portla7id Cement. 5 

When the cement is formed with too small a 
proportion of clay, the excess of lime remains in 
it as free lime and constitutes one of the chief 
dangers in the use of cement, as, although it will 
not prevent the proper action of the cement when 
used, a very small percentage of free lime may 
be sufficient to cause the mortar to afterward 
swell and become cracked and distorted. This is 
due to the increase of volume caused by the slak- 
ing of the lime by the water. When the free 
lime is in ver}^ small quantity the slaking will 
not take place until after the hardening of the 
mortar, and then becomes a strong disrupting 
.force. 

Professor Le Chatelier, who has made a ver}^ 
careful study of the nature and action of Portland 
cement, gives two limits within which the quan- 
tity of lime in the cement must always be found. 
These are, that the proportion of lime should 
always be greater than that represented b}^ the 
formula : 

I Cap + MgO _ 

SiO. - A1.A —FeOs ^' 

In which the symbols represent the number of 
equivalents of the substances present, and that it 
should never exceed that given by the formula: 

^ Cap -f MgO _ 

' SiP. + Al.Po - FeP ^ 



6 Hydraulic Cement. 

This is based upon the theory that the essential 
ingredients of the cement are the silicate of lime 
of formula sCaO, Si02, the aluminate of lime of 
formula sCaO, AI2O3, and the silico aluminate of 
formula 3CaO, AI2O3, 2 SiO^. Of these, the first 
two are the active elements of the cement, the 
third being inert in the cement, but being first 
formed in the burning and acting as a flux to fa- 
cilitate the combination of the silica and lime. 

Formula i represents the point at which the 
amount of lime present would be just sufiicient 
to form the tricalcic silicate and the silico- 
aluminate, no aluminate being formed. If less 
lime than this be present the bicalcic silicate 
(2CaO, 3102) would be formed, which powders 
upon cooling in the furnace and does not possess 
the power of hardening in contact with water. 

Formula 2 represents the point at which the 
amount of lime would be sufiicient to form the 
tricalcic silicate and tricalcic aluminate, to the 
exclusion of the silico aluminate. If more lime 
than this be present it will remain in the form of 
free lime. It is necessary to keep well within 
these limits as the mixture will necessarily be 
somewhat imperfect. 

It is also stated by Professor Le Ch atelier that 
for Portland cement of good quality formula i 
usually gives 3.5 to 4 and formula 2 gives 2.5 to 
2.7 as a result. 



Natural Cement. 7 

Free lime in the cement may also result from 
the lack of uniformity in the incorporation of the 
ingredients, or from underburning. In this case 
the process of combination is not complete, and 
the free lime and bicalcic silicate may exist at the 
same time in the cement. 

ART 3. NATURAI, CKMENT. 

Natural cements are those which are made by 
burning a limestone which naturally contains the 
proportions of silica and other ingredients neces- 
sary to cause it to harden under water when 
made into mortar. 

These cements are now made in considerable 
quantities in many places throughout this 
country, and differ very widely in composition 
and value. As in the case of a Portland cement, 
the making of a good natural cement implies 
care in the selection of materials, and frequently 
the admixture of various portions of the rock 
used is necessary to the production of a cement 
of uniformly good quality. The one class may 
thus merge into the other, and the classification 
of some becomes doubtful. 

There is considerable confusion in the use of 
terms to designate the various kinds of natural 
cement. In general they may be disiinguished 
in this country by a name derived from the 



8 Hydraulic Cemetit. 

locality in which they are manufactured, but 
greater uniformity of nomenclature would be ad- 
vantageous as conducing to a better understand- 
ing of the characteristics of the material. 

American natural cements may perhaps be 
divided into three general classes, natural Port- 
land cements, magnesian cements and aluminous 
cements. 

Those natural cements which possess about 
the normal composition of an artificial Portland 
cement are sometimes designated natural Port- 
land cements. In Europe cements of this char- 
acter are usually grouped under the name of slow 
setting natural cements. In common with nearly 
all natural cements, these possess usually a higher 
hydraulic index than the artificial Portland ce- 
ments. They show in general characteristics sim- 
ilar to those of the artificial Portlands, and are 
usually more heavily burned than other grades of 
natural cement. 

The magnesian cements are those in which a 
portion of the lime of the Portland is replaced 
by magnesia. These cements are also lighter 
burned and have a higher hydraulic index than 
Portland cements. The Rosendale cements are a 
class of natural cements made from a magnesian 
limestone found abundantly along the Hudson 
River. The term Rosendale is sometimes applied 
in a general way to all American natural cements, 



Natural Cement. 9 

but it is more properly restricted to those from 
the locality of the lower Hudson, and of the 
magnesian variety. 

The composition and characteristics of cement 
of this class vary considerably, even in the same 
locality, according to the strata from which the 
rock is obtained and the care used in selecting 
and manipulating it. The quantit}^ of magnesia 
in it varies from about 10 per cent to 25 per cent. 
The Utica cements of Illinois also belong to this 
class, with several other Western makes. 

Cements of the aluminous variety are known in 
Europe as quick setting natural cements, or 
Roman cements. They differ from Portland 
cement in having a higher hydraulic index, and 
in containing more alumina. They also usually 
contain a higher percentage of sulphuric acid 
than the other varieties, but not always. The 
Louisville cements may be placed in this class. 

Between these two latter classes of cements, 
are a number of varieties which gradually merge 
the one into the other. These contain a higher 
percentage both of alumina and of magnesia 
than the Portlands. They are widely scattered 
throughout the country and vary greatly in their 
composition and characteristics, some being 
noticably low in their amount of lime, and others 
containing considerable quantities of iron oxide. 



lo Hydraulic Cement. 

To this general description the larger number of 
American natural cements belong. 

ART. 4. SI.AG CKMKNT. 

Slag cements are those formed by an admixture 
of slaked lime with ground blast furnace slag. 
The. slag used has approximately the composition 
of an hydraulic cement, being composed mainly 
of silica and alumina, and lacking a proper pro- 
portion of lime to render it active as a cement. In 
preparing the cement, the slag upon coming from 
the furnace is plunged into water and reduced to 
a spongy form from which it may be readily 
ground. This is dried and ground to a fine 
powder. The powdered slag and slaked lime are 
then mixed in proper proportions and ground 
together, so as to very thoroughly distribute them 
through the mixture. It is of first importance in 
a slag cement that the slag be very finely ground 
and that the ingredients be very uniformly and 
intimately incorporated into the mixture. 

Both the composition and methods of manu- 
facture of slag cements vary considerably in 
different places. They usually contain a higher 
percentage of alumina than' Portland cements, 
and the materials are in a different state of com- 
bination, as, being mixed after the burning, 
the silicates and aluminates of lime formed 



Setting of Cemeyit. 1 1 

during the burning of Portland cement cannot 
exist in slag cement. 

Other mixed cements are sometimes made in 
Europe using different material of the same 
general nature as the slag. Puzzuolana cements 
are those made by a mixture of volcanic ashes 
with lime, although the name is vSometimes ap- 
plied to mixed cements in general. The use of 
puzzuolana has been known for man}^ years in 
Europe, and dates back to the time of the 
Romans. A volcanic earth called trass is also 
frequently employed for this purpose. The slag 
cements are, however, the only important ones of 
this nature, the others being of limited applica- 
tion. 

ART. 5. SETTING OF CEMKNt. 

When cement powder is mixed with water to a 
plastic condition, and allowed to stand, it grad- 
ually combines into a solid mass, taking the water 
into combination, and soon becomes firm and 
hard. This process of combination amongst the 
particles of the cement is known as the setting of 
the cement. 

Cements of different composition differ very 
widely in their rate and manner of setting. Some 
occupy but a few minutes in the operation, and 
others require several hours. Some begin setting 
immediately and take considerable time to com- 



12 'Hydraulic Cement. 

plete the set, while others stand for a considerable 
time with no apparent action and then set very 
quickly. 

The points where the set is said to begin and 
end are necessarily arbitrarily fixed, and are dif- 
ferently determined, usually by trying when the 
mortar will sustain a needle carrying a given 
weight. The point at which the set is suppOvSed 
to begin is when the stiffening of the mass first 
becomes perceptible, and the end of set is when 
the cohesion extends through the mass sufficiently 
to offer such resistance to any change of form, as 
to cause rupture before any perceptible deforma- 
tion can take place. 

It is sometimes stated that the chemical change 
involved in setting is an instantaneous occurrence 
at about the time we call the beginning of set, 
and that the gradual hardening then begins and 
is a continuous process until the maximum 
strength is reached. However this may be, with 
some cements a quite noticable change suddenly 
shows itself at about this time, in the disappear- 
ance of water from the surface of the mortar and 
the sudden stiffening of the mass. 

Professor I^e Chatelier in his study of Portland 
cements explains the phenomena of setting, by 
showing that certain salts, including the alumi- 
nate and silicate of lime which form the active ele- 



Setting of Cement. 13 

mentsof Portland cement, are much more soluble 
in an anhydrous than in a hydrated condition. 

When the}^ first come into contact with water, 
as in mixing the mortar, the anhydrous salt enters 
at once into saturated solution. In a short time 
by contact with the water the salt becomes hy- 
drated, and the h^^drated salt being less soluble is 
precipitated in a crystalline form. 

With the aluminate of lime this action is espe- 
cially rapid, and therefore as might be expected 
cements containing considerable proportions of 
this salt are more quick setting than others ; ce- 
ments with a low hydraulic index are apt to be 
quicker setting than those of the same class with 
a high one ; cements with a considerable propor- 
tion of alumina to silica are apt to be quicker set- 
ting than those with a less one. It is to be ob- 
served however, that an anal3^sis of a cement giv- 
ing the elements of its composition does not show 
the state of combination, and nothing can be nec- 
essarily inferred from a knowledge of such com- 
position as to its action in setting. Thus, an 
underburned cement will set more quickly than 
the same cement thoroughly burned, and slag 
cement, while usually showing a high percentage 
of alumina, is generally slow in setting. 

It is not correct to state as is commonly done 
that natural cement is quick setting and Portland 
cement slow setting. The aluminous natural ce- 



14 Hydraulic Cement. 

ments are commonly quick setting, though not 
always so, as those with a high hydraulic index 
or containing a considerable percentage of sul- 
phuric acid may set quite slowly. The magnesian 
and Portland varieties may be either quick or slow. 
Specimens of either variety may be had that will 
set at any rate, from the slowest to the most rapid, 
and no distinction can be drawn between the 
various classes in this regard. 

The age of a cement affects the rate of setting 
to some extent. This is especially liable to be 
the case with quick setting cements when they 
are exposed to dry air. Such exposure makes 
the vSetting slower. A slow setting cement of 
good quality is generally less affected, if affected 
at all. When the air to which cement is exposed 
is quite moist it may gradually absorb water until 
it is practically ruined, and will not set at all. 
Where the cement is kept in tight barrels, its age 
is not usually of so much consequence, unless it 
be exposed to dampness, which may penetrate 
the barrels and cause it to become hard prema- 
turely. 

Fine grinding, to some extent, accelerates the 
setting of a cement. 

The time occupied in setting is also affected by 
various external circumstances under which the 
cement is used. The effect upon different kinds 



Setting of Cement. 15 

of cement is very different in degree, old cements 
being generally less affected than fresh ones. 

The quantity of water M'^^^ in mixing the mortar 
is one of the most important conditions, the less 
the quantity, provided there be sufficient to 
thoroughly dampen the mass of cement, the 
quicker will be the set. With some Portland ce- 
ment, changing the quantity of water used in 
mixing neat cement from 20 per cent, to 25 per 
cent, of the w^eight of cement, will double or even 
triple the time necessary for the mortar to set. In 
other cases the effect is comparatively slight. 

The nature of the water used in mixing may al- 
so affect the rate of setting. When sea water is 
used the setting is usually slow^er than with fresh 
water, the chloride and sulphate of magnesia being 
the principle retarding elements. Cements with 
a high hydraulic index will show a less difference 
between fresh and sea water than those of the 
same class with a low one, and well burned ce- 
ments less than imperfectly burned ones. The 
experiments of M. Candlot indicate that this is 
due to the action of the salts mentioned above 
upon the aluminate of calcium, and that those 
cements containing the highest percentage of 
aluminate are affected the most, by being mixed 
with sea water. 

Water containing sulphate of lime in solution 
retards the setting of cement. This fact has been 



1 6 Hydraulic Cement, 

made use of to some extent in Europe in the 
adulteration of cement, powdered gypsum being 
mixed with it to make it slow^ setting, greatly to 
the injury of the material. 

The temperature of the water used in mixing has 
an important bearing upon the time required for 
setting, the higher the temperature, within cer- 
tain limits, the more rapid the set. Many cements 
which require several hours to set when mixed 
with water at a temperature of 40° Fahr. , will set 
in a few minutes if the temperature of the water 
be increased to 80° Fahr. Belov/ a certain in- 
ferior limit, ordinarily from 30° to 40° Fahr. , the 
mortar will not set, while at a certain upper limit, 
in many cements between 100° and 140° Fahr., a 
change is suddenly made from a very rapid to a 
very slow rate, which then continually decreases 
as the temperature increases, until practically the 
mortar will not set. 

The temperature of the cement, and that of the 
air in which the mortar is placed during setting, 
influence the rate of setting in about the same 
manner as that of the water. In case the air in 
which the mortar is placed be dry, the setting 
will usually be somewhat more rapid than if it be 
moist, and if it be too dry, the rapid evaporation 
of the water from the surface of the mortar may 
cause drying cracks in the mortar. 

Quick setting cements usually show a rise of 



Hardening of Cement. 17 

temperature during setting, due to the rapidity of 
the action which takes place. It has been sug- 
gested that the time occupied by the setting would 
be better shown by observing the period of ad- 
vanced temperature, than by noting the stiffening 
of the mortar, as is now done. Most slow setting 
cements however do not show sufficient change 
of temperature, if any takes place, to be appre- 
ciable, and the rise of temperature, where it does 
take place, may not in all cases be the result of 
the process of setting. 

ART. 6. HARDENING OF CKM^NT. 

After the completion of the setting of the ce- 
ment, the mortar continues to increase in cohesive 
strength over a considerable period of time, and 
this subsequent development of strength is called 
the hardening of the cement. 

The process of hardening appears to be quite 
distinct from, and independent of that of setting. 
A slow setting cement is apt, after the first day or 
two, to gain strength more rapidly than a quick 
setting one, but it does not necessarily do so. 
The ultimate strength of the cement also, is quite 
independent of the rate of setting. A cement 
imperfectly burned will set more quickly and gain 
less ultimate strength than the same cement 
when properly burned, but of two cements of dif- 



1 8 Hydraulic Cement. 

ferent composition the quicker setting may be the 
stronger. 

There is as wide a variation in the rate of hard- 
ening attained by different cements as in the rate 
of setting ; some gain strength rapidly and attain 
their ultimate strength in a few days, while others 
harden more slowly at first and continue to gain 
in strength for several years. The rate of early 
hardening gives but little indication of the ul- 
timate action of the cement, as the final 
strength of the mortar may be the same, however 
rapidly the strength is attained. Portland ce- 
ment usually hardens more rapidly and gains its 
maximum strength more quickly than natural 
cement, and also as a rule the Portland cement 
will attain greater strength when used in the 
same manner. Of two cements of the same class, 
however, it is not safe to infer that that which 
most rapidly gains strength will prove the 
stronger and more permanent material ; in fact, 
where an abnormally high strength is shown in a 
few days, the presumption as to the probable final 
strength should be against the cement giving 
such result and in favor of one hardening at a 
more moderate rate. 

The rate at which cement should harden for a 
given use, depends, of course, upon the necessity 
of developing early strength in the work. For 
many purposes, such as most sub-aqueous con- 



Hardenijig of Cement. 19 

struction, such early strength is highly desirable 
if not necessary, but for most engineering work a 
very rapid hardening does not seem necessary and 
better results may often be obtained by the use of 
a material of more gradual action. 

Cements with a low hydraulic index com- 
monly harden more rapidly than those with a 
high one. When the material is somewhat over- 
clayed the hardening becomes slow, and if this 
effect be considerable, the material shows a very 
low earl}^ strength and is commonly considered 
worthless, but may continue to gain in strength 
over a very long period and ultimately make a 
hard and durable mortar. 

Where the cement is overlimed it is likely to 
gain strength very rapidly in the beginning, and 
later to lose its strength, or, if the percentage of 
free lime be sufficient it will ultimately disinte- 
grate. When the mortar is immersed in sea 
water this disintegrating action is more rapid 
than when it is kept in fresh water. 

Fz7tely ground Q^m^nis, mixed neat, will harden 
more rapidly than when coarsely ground, but will 
not usually reach so high a degree of final 
strength . When mixed with sand the fine cement 
will reach the greater strength. 

Effect of Sand. Cement is generally used in a 
mortar mixed with a certain proportion of sand, 



20 Hydraulic Cement, 

and the action of the mortar is necessarily largely 
affected by the nature and quantity of the sand 
used. 

When the cement is finely ground and the sand 
of good quality, a mortar composed of equal 
parts of each will, as a general thing, finally at- 
tain a strength as high as, or higher than that of 
the neat cement. Cements of different charac- 
ters, however, vary considerably in their power to 
take sand without loss of strength ; some of the 
weaker ones may not be able to take more than 
half their weight of standard sand, while others 
can be mixed with considerably more than their 
own weight, without loss of strength at the end 
of twelve months after mixing. All have a cer- 
tain limit within which they may be made 
stronger by an admixture of good sand than they 
would be if mixed neat. 

Cement mixed with sand will always harden 
more slowly than neat cement, and require a 
much longer time to attain its maximum strength. 
As the proportion of sand to cement is increased 
both the rate of hardening and final strength of 
the mortar are diminished. 

The finer ground the cement, the greater will 
be its resistance when mixed with sand, both in 
the earlier and later stages, and also the sooner 
will it reach its ultimate strength. The effect of 
fine grinding is much greater where the propor- 



Hardejiing of Cement. 21 

tion of sand to cement in the mortar is large, as 
the power of the cement to take sand without di- 
minution of strength is thereby greatly increased. 
The coarser particles of the cement may be con- 
sidered as practically inert material, which acts 
rather as sand than as cement in the mortar, and 
the power of the cement to harden and develop 
strength, when mixed with sand, is dependent 
upon the amount of fine material contained in it. 

Clean and sharp sand will always give a higher 
strength in mortar than that containing an ad- 
mixture of clay or earth, or that composed of 
rounded grains. 

Coarse sand will also give greater strength than 
that which is very fine. 

Quantity and Nature of Water, When the 
quantity of water used in mixing is sufficient to 
reduce the mortar to a soft condition, the harden- 
ing as well as the setting becomes more slow, and 
the strength during the early period is much less, 
than if a less quantity be used. This difference 
in strength disappears to some extent with time, 
and the mortar mixed wet may eventually gain 
nearly as much strength as though mixed with 
less water. 

When the quantity of water used is not suffi- 
cient to reduce the mass to a plastic condition, 
the mortar will not be so thoroughly compacted, 
and will not reach the same strength as when 



22 Hydraulic CeTuent. 

made plastic, unless pressure be applied to it. 
But if just sufficient water be used to thoroughly 
dampen the mortar, 'and pressure be applied to 
expel the air and close the voids, the early 
strength will be greater than when more water is 
used. This difference, like the former one, dis- 
appears to a certain extent with time, but the 
final strength is usually greater with the less 
quantity of water. 

Mortar kept immersed in sea water usually 
hardens more rapidly than that kept in fresh 
water. This difference is commonly much more 
noticable with neat cement than with mortar con- 
taining considerable proportions of sand. 

Cements with a low hydraulic index show the 
greatest difference between sea and fresh water. 

Cements containing small quantities of free 
lime give much greater early strength in sea than 
in fresh water, but are also sooner disintegrated 
by the sea water. 

The nature of the water with which the mortar 
is mixed is not of so great importance as that of 
the water in which it is allowed to harden. When 
the mortar is to be kept in air, the nature of the 
water used in mixing becomes more important, 
although probably the variations in ordinary nat- 
ural water are rarely sufficient to produce any ap- 
preciable difference in the strength of the mortar. 

Cement kept under water hardens more rapidly 



Hardening of Ceinent. 23 

at first than that exposed to the air, but usually, 
that kept in air will ultimately reach greater 
strength. The highest strength will ordinarily 
be produced by keeping the cement during the 
early period in water or at least in very moist air, 
and later in dry air. Nearly any cement mortar 
will harden more rapidly and attain greater 
strength if kept moist during the operation of 
setting and the period of early hardening than if 
it be exposed at that time to dry air. 

Effect of Temperature. The temperature of 
the water with which cement mortar is mixed has 
a quite appreciable effect both upon its rate of 
hardening and its ultimate strength, and the 
temperature of the air at the time of mixing has a 
similar effect. The lower the temperature at which 
the mixing is done, the slower will be the harden- 
ing, and the greater will the final strength be. 
This difference is not sufficient to be important at 
ordinary air temperatures in so far as the use of 
the mortar is concerned, but is quite appreciable 
in making comparative tests. 

If the air at time of mixing be sufficiently cold 
to freeze the mortar before it can set, it will not 
set while frozen, but most cements will do so after 
thawing out, and but few of them will be injured 
by such freezing in so far as their strength is con- 
cerned. 



24 Hydraulic Cement, 

The temperature of the air or water in which 
the mortar is immersed during the time of hard- 
ening has a very appreciable effect upon the rate 
* of hardening of many cements. This effect differs 
very radically for different material; with some the 
process is greatly accelerated by keeping them 
hot as compared with what would be the result in 
cold air or water; others are not appreciably af- 
fected, while still others seem to be retarded in 
their hardening by the application of heat. This 
variation is to be found among cements of the 
same class, and is seemingly independent of their 
value. Cements with a low hydraulic index usu- 
ally show the greatest gain in rate of hardening 
under the action of heat* 

1 ART. 7. ADHESION. 

For most of the ordinary uses to which cement 
mortar is put, its power of adhering to the 
surfaces with which it is placed in contact is of 
greater consequence than is its cohesive vStrength. 
This power of adhering to other material is very 
highly developed in a good cement, but its exact 
evaluation is a matter of considerable difficulty 
on account of the many circumstances that may 
operate to affect it. It has been found in general 
that the cohesive and adhesive strengths vary in 
somewhat the same manner for different material, 



Adhesion. 25 

and the determination of cohesive strength is 
commonly relied upon as a test of value. 

The strength of a mortar composed of cement 
and sand, calls into play the adhesion of the 
cement to the sand as well as the cohesive 
strength of the cement itself, and the larger the 
proportion of sand the greater the dependence 
upon adhesion. An idea of the value of the ad- 
hesive power of the cement may therefore be ob- 
tained by observing the comparative strengths of 
mortar made from neat cement, and that com- 
posed of cement and sand in varying proportions. 

The adhesion of mortar to any surface to which 
it may be applied will depend upon the nature 
and condition of the surface, being greater as the 
material is more hard and non-porous. The 
adhesive strength unlike the cohesive strength 
will be greater as the mortar is made more wet, 
or when mortar of ordinary consistency is in use, 
the adhesive strength will be greater if the 
surface to which it is to be applied is first 
thoroughly dampened. 

The fineness of the cement has an important 
effect upon adhesive strength, the finer the 
cement the greater its adhesive strength. A 
mortar composed of cement and sand will also 
possess greater power of adherence when coarse 
sand is used than when the sand is fine. 



26 Hydraulic Cement. 

ART. 8. PKRMANKNCK OF VOI.UME OR SOUNDNESS. 

The permanence of any structure, erected by 
the use of cement, is dependent upon the power of 
the cement, after the setting and hardening pro- 
cesses are complete, to retain its strength and form 
unimpaired over an indefinite period. Experi- 
ment has shown that mortars made from cement 
of good quality frequently continue to gain in 
strength and hardness through a period of several 
years, or at least that there is no material diminu- 
tion of strength with time, and that changes of 
temperature, or in the degree of moisture sur- 
rounding it, produce no injurious effect upon the 
material. This durability of the material in use is 
commonly known as the permanence of volume or 
the soundness of the cement. 

Heat has the same effect to expand and contract 
cement mortar of good quality as it has upon other 
materials. The coefficient of expansion for neat 
Portland cement mortar according to a series of 
experiments at ' ' 1' Ecole des Fonts et Chaussees, ' ' 
is about the same as that of iron. For sand 
mortar the coefficient is somewhat less. 

When mortar which has been immersed in 
water is transferred to dry air, a slight contraction 
may take place in volume, together with an in- 
crease in strength, while a transferrence the 
other way may produce the opposite result, but 
no distortion of form or disintegration of the 



Permane7ice of Volume or Soicndness, 27 

mortar will take place in either case if the 
cement be of good quality. 

Sometimes cement when made into mortar sets 
and hardens properly, and later, when exposed to 
the action of the atmosphere or water, becomes 
distorted and cracked, or even entirely disinte- 
grated. If the composition deviates but slightly 
from the normal, this process of disintegration 
may not show itself for a considerable time and 
proceeds very slowly. It thus becomes an ele- 
ment of considerable danger as it is liable to 
escape detection in testing the cement. The most 
common cause of this unsoundness is probably 
the existence of vSmall quantities of free lime or 
magnesia in the cement. Magnesia in Portland 
cement is from this cause always an element of 
danger, and should not be present in a quantit}^ 
exceeding about 3 per cent. In many natural 
cements, however, magnesia replaces a portion of 
the lime when the cement is of normal com- 
position, and does not render the cement unsound, 
unless, like the lime, it is in excess. 

The presence of sulphate of lime in any con- 
siderable quantity also commonly produces un- 
soundness in the cement, and for that reason an 
analysis of the cement should usually show but 
a very small percentage of sulphuric acid ; for 
Portland cement, the limit is about one per cent. 
There are, however, cements in which a larger 



28 Hydraulic Cement. 

percentage of sulphate occurs normally and does 
not produce unsoundness ; these are, according to 
M. Candlot, usually the ones containing a high 
percentage of alumina. 

The presence of aluminate of lime is also said 
to be a cause of unsoundness where cement mortar 
is to be used in sea water, and Portland cement 
for such use should contain as high a percentage 
of silica in proportion to the alumina as possible. 

With most unsound cements the disintegrating 
action is more rapid at high than at low temper- 
atures. Sea water usually causes more rapid dis- 
integration than fresh water. 

The term, permanence of volume, if limited to 
the power of the material to resist actual change 
of form, or dimension, in the body of mortar, is 
not necessarily synonomous with soundness, if, by 
soundness, we designate its power to resist disin- 
tegration over a long period. Most unsound ce- 
ments fail by swelling and cracking, after which 
disintegration occurs. This is especially apt to 
be the case with those containing an appreciable 
percentage of free lime or magnesia, the failure 
occurring in a comparatively short time. In 
some other cements, however, the failure occurs 
by a gradual softening of the mass of mortar, 
without appreciable change of form or dimension, 
the process being very slow, sometimes not notice- 
able for several months after the mortar is mixed. 



CHAPTER II. 

METHODS OF TESTING CEMENT. 



ART. 9. OBJKCT OF TESTING. 

The testing of cement usually differs from the 
testing of other materials of construction, in that 
the test is intended to determine whether the 
material tested be of good quality, and not as a 
measure of its actual strength in use. Cement is 
not commonly employed where it is subjected to 
stresses nearly approaching its limit of safe 
strength, and a knowledge of just what that 
strength ma}^ be, is not ordinarily of so much 
consequence. What we want to know about the 
cement is that it will set and harden into a solid 
mass, which will firmly adhere to any surface 
with which it may be in contact, and that it will 
endure through a long time, without change of 
form or loss of solidity. 

As ordinary tests must be made in a short time, 
but a few days at most being usually allowed for 
determining the quality of the material, the prob- 
lem to be met in testing is to apply such tests, as 
will enable a prediction to be made, from its be- 
havior under them in a short time, what it will 
do in a long time under the circumstances of its 
use. The difficulty of this with a material vary- 



30 Hydraulic Cement. 

ing so widely in its character, and in its behavior 
under various conditions, is evident. If we have 
a particular brand of cement whose characteristics 
we know, we may readily determine whether a 
given sample is of normal quality, and predict 
something of its future from its behavior under 
short time tests. Very little, however, can be 
done in the way of generalization, and for a new 
or unknown material we can only state a some- 
what indefinite probability as to final results. 

Tests may be imposed which in nearly all cases 
will secure good material, but at the expense 
many times of rejecting equally good or better 
material. This, however, will be unavoidable 
until such time as the characteristics of the vari- 
ous makes of cement are more fully known, and 
the tests to which each should be subjected better 
understood. The individuality of the cement is 
a very important factor. 

The tests, which are usually impo.sed to deter- 
mine the quality of hydraulic cement, are those 
of weight, fineness, time of setting, tensile 
strength and soundness. Chemical analysis is 
sometimes made, and specific gravity test is sub- 
stituted for that of weight, or both are frequently 
omitted. Compression tests are also sometimes 
added. 

The greatest weight is usually given to the test 
of tensile strength, and much greater value is 



Object of Testing. 3 1 

commonly placed upon the results of that test 
than they deserve. It is much the simplest and 
best means of making a test for strength, and is 
very desirable as showing the proper hardening 
of the mortar, but cements cannot be graded in 
value by the strength attained in a short time. 
A cement giving a very high early strength is to 
be relied upon, only in so far, as it has been 
shown by experience capable of subsequently 
maintaining such strength. The attempt to pro- 
duce a cement, which will develop great strength 
in a vShort time, is liable to result in a lowering of 
the hydraulic index, and frequently in the pres- 
ence of free lime, giving a material more likely to 
be unsound than one of more moderate strength. 

The test for soundness or permanence of volume 
is a very important one, as giving an indication 
of the probable durability of the material, but in 
this as in all other cases, a knowledge of the nor- 
mal action of the material will contribute greatly 
to the proper interpretation of the test. 

The test for fineness is also important as show- 
ing the power of the cement to take sand. 

It is recommended by the Committee of the 
American Society of Civil Engineers upon a uni- 
form system of testing, that tests for quality be 
limited to the above three most important tests, 
fineness, tensile strength and soundness, and this 
recommendation is now commonly followed in 



32 Hydraulic Cement, 

this country, although the test for soundness as 
usually made is of little value. 

ART. lO. TESTS FOR WEIGHT AND SPKCII^IC GRAVITY, 

The determination of the weight of a given 
volume of the cement to be tested, is frequently 
made for the purpose of obtaining an idea as to 
whether the cement is properly burned. An un- 
derburned cement is somewhat lighter in weight 
than if thoroughly burned. 

The weight of the cement will also depend 
upon the fineness to which it is ground, the 
coarser the particles of the cement the heavier it 
will be ; therefore when a weight test is included 
in a specification, a test for fineness must also be 
included, to prevent the attainment of weight by 
coarse grinding. 

The weight test is not now commonly employed 
in tests for quality, as it is indefinite both in its 
execution and in the interpretation of its results, 
and other tests are of more importance in deter- 
mining the value of the material. 

As the cement powder may be packed so as to 
give very different weights for the same volume, 
it is necessary to use a uniform system of filling 
the measure in determination of weight. The 
common method of conducting the test is, to sift 
the powder through a coanse sieve and allow it to 
fall through a funnel or down an inclined slide 



Tests for Weight and Specijie Gravity. 33 

through a given height into the measure The 
height of fall and the size of the measure will 
both affect the result, the cement packing closer 
in a large than in a small measure. 

In France the standard method of testing 
weight is to sift the cement through a sieve of 
5000 meshes per square centimeter, and weigh only 
the powder which passes that sieve. After pass- 
ing the sieve, the powder falls upon a metal slide, 
or square trough, one-half meter long and inclined 
at an angle of 45° with the horizontal. The ma- 
terial slides down this trough and into a measure 
holding a litre, the top of which is placed one cen- 
timeter below the bottom of the trough. When 
full the measure is struck and weighed. 

The advantage of this method is that it makes 
the weight to a certain extent independent of 
fineness. In American and English practice there 
has been no uniformity in the methods employed 
in different laboratories for determining weight. 

The ordinary weight of Portland cement varies 
from 70 to 100 pounds per cubic foot. Natural 
cements are usually somewhat lighter. 

The determination of specific gravity is often sub- 
stituted for that of volume weight, and is a better 
guide to a knowledge of actual density. The 
differences of specific gravity are, however, so 
small as to require very accurate determinations 
of its value. 



34 Hydraulic Cement. 

The specific gravity of Portland cement of 
good quality varies from 3.05 to 3.20 and is usu- 
ally above 3. 10. That of natural cement varies 
from about 2.70 to 3.10. A difference in density 
may be caused by variation in composition, as 
well as in the degree of calcination of the mate- 
rial, and therefore the greater density does not of 
necessity represent the best preparation of the 
cement. 

The test for specific gravity is commonly made 
by immersing a known weight of the cement in 
a liquid which will not act upon it, and obtaining 
its volume by observing the rise in the surface of 
the liquid. 

Care must be taken in immersing the cement 
to permit the escape of the air bubbles contained 
in it, either by sifting the powder through the 
liquid, or if the powder be first placed in the ap- 
paratus and the liquid afterward introduced, by 
agitating until the liquid is thoroughly distributed 
through the cement and then allowing the mass 
to settle. 

If a tube graduated to cubic centimeters be en- 
larged to a ball at its lower end, or be attached 
to a dish at its lower end, and this tube be filled 
with benzine to a height at which a reading may 
be taken on the tube, and a given weight of 
cement (as 100 grammes) be sifted through the 
tube into the dish or ball below, and a second 



Test for Fine7iess. 35 

reading taken on the tube at the surface of the 
Hquid, the difference between the two readings 
will be the actual volume of cement in cubic cen- 
timeters, then, weight in grammes divided by 
volume in centimeters gives directly the specific 
gravit3^ The Schuman Volumenometer works 
upon this principle. Several other forms use a 
somewhat similar apparatus, but first place the 
cement in the apparatus, then pour a known 
quantity of liquid over it, depending upon agi- 
tating the apparatus sufficiently to eliminate the 
air bubbles from the cement powder. 

ARl". IT. TEST FOR FINENESS. 

The fineness to which a cement is ground is 
always a matter of importance, as upon it 
depends very greatly the adhesive power of the 
cement, and its ability to take sand. A test for 
fineness is nearly always given in specifications 
for cement, and this test is of most importance 
when, as is very commonly the case, the tensile 
strength is tested for neat cement only. In this 
case, the attainment of a proper strength neat, 
together with a fair degree of fineness, practically 
insures that the cement will give good results 
when used with sand. 

The fineness which should be required in a 
cement is largely a question of relative economy ; 
the finer ground the cement, the larger the quan- 



36 Hydraulic Cement, 

tity of sand that may legitimately be used with 
it. All the coarse parts of the cement are to be 
considered as inert material, or practically as a 
certain amount of sand already mixed with the 
cement, and the problem, in deciding upon a re- 
quirement as to fineness, may become that of 
determining whether it will be cheaper to pay a 
higher price for the cement, or use more of it. 

The test for fineness simply consists in sifting 
the cement through a sieve, or a set of sieves, 
and observing the amount retained by each sieve. 

The committee of the American Society of Civil 
Engineers upon standard tests, recommend the 
use of sieves of 2500, 5476, and loooo meshes per 
square inch. Specifications usually, however, 
require only a single sieve, generally that of 2500 
meshes, but sometimes that of loooo meshes. A 
more general use of the finer sieve would un- 
doubtedly be advantageous, as it is now generally 
admitted that all material coarser than that di- 
mension is practically inert, and a real measure 
of useful fineness is not given by the 2500 mesh 
sieve. A common requirement is, that not more 
than 10 per cent, by v/eight of the cement be re- 
tained upon a sieve of 2500 meshes, or that not 
more than 20 per cent, be retained upon that of 
1 0000 meshes, or both. Most of the cements 
commonly in use in this country easily comply 
with these requirements ; many of the best ones 



Test for Fineness. 37 

do not give a residue on the coarse sieve of more 
than I to 3 per cent. , or on the fine one of more 
than 8 to 12 per cent., natural cements being 
usually finer than Portland. Some brands of 
Portland cement, however, seem to be prepared 
with special reference to meeting the requirement 
of the 2500 mesh sieve, and are very coarse when 
tested with a finer one. 

In France and Germany sieves of 324, 900 and 
5000 meshes per square centimeter are employed. 
The present requirements in Germany and 
Switzerland are that not more than 15 per cent 
shall be retained on the sieve of 900 meshes per 
square centimeter. 

The size of wire of which the sieve is made is 
of course important as regulating the size of 
openings and should always be stated, the com- 
mon standard is that the diameter of the wire 
should be about Yz of the spacing between 
centers. It is not commonly possible to get 
sieves with perfect regularity either of spacing or 
diameter of wires, a sufficiently near approx- 
imation for practical work may be obtained 
by using care in selecting the sieve, but the 
gauze frequently offered for this use differs very 
widely in the sizes of openings for the same num- 
ber per inch, and sometimes the openings are 
quite irregular in size in diff'erent parts of the 
same sieve. 



38 Hydraulic Cemefit, 

ART. 12. RATK OF SETTING. 

The rate of setting of cement is tested for the 
purpose of determining if it be suitable for a given 
use, and not as a measure of the quality of the 
material. For most purposes, where immediate 
setting is not required to prevent disturbance of 
the mortar before hardening, the moderately slow 
setting cements are found more convenient, as 
they need not be handled so quickly and may be 
mixed in somewhat larger quantities. 

Testing for time of setting consists in arbi- 
trarily fixing two points in the process of con- 
solidation which are called the beginning and 
the end of set. These points are differently de- 
termined in the different systems of testing. 

The method recommended by the committee of 
the American Society of Civil Engineers is that 
proposed by General Gillmore, and consists in 
mixing cakes of neat cement, about 2 or 3 inches 
in diameter and ^ inch thick, to a stiff plastic 
consistency, observing the time when they will 
bear a needle -^^ inch in diameter sustaining a 
weight of % pound, and noting this as the be- 
ginning of setting ; then continuing the observa- 
tions with a needle -^^ inch in diameter carrying a 
weight of one pound until the material is suffi- 
ciently firm to bear this when it may be called fully 
set. The committee call all those cements which 



Rate of Settirig. 39 

set in one-half hour or less quick setting, those 
requiring more time slow setting. This method 
and nomenclature are commonly followed in this 
country. 

In Germany and France the method commonly 
followed for accurate determination is that of the 
Vicat Needle. By this method a briquette of 
neat cement is made in a cylindrical bravSS or 
rubber mold, 10 cemtimeters in diameter and 4 
centimeters high, placed upon a plate of glass or 
metal, the cement being mixed to a plastic con- 
dition as determined by the consistency test. 
The apparatus is so arranged that a weight of 300 
grammes may be brought either upon a needle of i 
millimeter diameter or upon a cylindrical plunger 
of I centimeter diameter, and allowed to settle into 
the cement, the depth of penetration being shown 
by a scale along which the weight slides. 

As soon as the mold is filled with the mortar, 
it is placed in the apparatus, and the plunger, 
sustaining the 300 grammes, is brought to the 
surface of the briquette and allowed to sink into 
it. If the plunger penetrates to a point 6 to 10 
millimeters from the bottom, the mortar is of 
proper consistency for the test. The needle is 
then substituted for the plunger, and the time 
when the needle first refuses to sink entirely 
through the mortar is observed and noted as the 
beginning of setting ; the time when the needle 



40 Hydraulic Ce^nent, 

first rests upon the briquette without penetrating 
it is considered the end of setting. This method 
gives slower results than the first one when the 
consistency is the same. It also gives more uni- 
formity of result when conducted by different 
persons. 

For ordinary practical purpOvSes the common 
method is sufficiently accurate as all that is nec- 
essary to know is whether the cement sets quickly 
or slowly, but for experimental and comparative 
purposes the more elaborate method is valuable. 
The beginning of set is the point of most value 
to determine, as the cement in practice should be 
used before that point is reached, in order that it 
may not be disturbed after the stiffening has be- 
gun. It would seem that this point is better 
shown by the Vicat Needle, but in practical use 
the cement should be tested mixed as used in the 
work. 

The time of setting is often roughly determined 
in practice, by making small cakes of mortar and 
observing when they will resist penetration under 
a light pressure of the thumb nail. This is a 
standard test in Germany. 

The change of temperature during setting is 
also commonly observed in the European labora- 
tories, and frequently in experimental work in 
this country. A rise in temperature, however, 
does not ordinarily occur except with quick ce- 



Testing Tensile Sti^ength. 41 

ments, and does not seem to have any relation to 
the value of the material. When a rise in tem- 
perature occurs with a slow cement, it is said to 
indicate unsoundness, but for very slow cements 
a rise seldom occurs, even with flagrantly un- 
sound material, which is appreciable upon a ther- 
mometer reading to one-fifth degree Fahrenheit. 
Time of setting is usually measured in the air 
at about 60° or 70° Fahr. for purposes of compar- 
ison, but in case the material is to be placed under 
water before setting, it should be tested under 
water. The effect of the circumstances of use 
upon the activit^^ of the material should always 
be tried when the conditions are unusual. 

ART 13. TESTING THK TENSIIvK STRENGTH. 

The tensile test is commonly used for the pur- 
pose of determining the strength of the cement 
mortar, because it can be more readily and uni- 
formly applied than any other, and seems, coupled 
with other tests, to give a fair indication of the 
value of the material. 

The proper conduct of a tensile test is a matter 
requiring care and experience. There are many 
points connected with the circumstances and mani- 
pulation of the test, which have an important 
bearing upon the result ; these are, the method of 
mixing and moulding the mortar, the form of the 
briquette, the amount and temperature of the 



42 Hydraulic Cement, 

water used in mixing, the temperature of the air 
at time of mixing, the temperature at which the 
briquette is kept during setting and hardening, 
and the rate and manner of applying the stress. 

Temperature. — In standard tests it is customary 
to adopt a nearly constant temperature of 6o°-65° 
Fahr. for the air of the laboratory during the 
making and setting of the briquettes, and about the 
same, or a slightly less temperature for the water 
used in mixing, and that in which the mortar is 
submerged during hardening. The effects of 
variations of temperature have been noted in 
Arts. 5 and 6. 

Methods of Making Briquettes. — The wide dif- 
ferences frequently observed in the results of dif- 
ferent experimenters are, without doubt, mainly 
due to personal differences in making the bri- 
quettes. These differences occur not only in the 
work of novices, but in that of skilled operators, 
who, while usually able to maintain practical 
uniformity in their own work, disagree in results 
with each other when experimenting upon the 
same material and apparently using the same 
methods. 

There are two methods in common use for mak- 
ing briquettes : the method recommended by the 
committee of the American Soicety of Civil En- 
gineers, which is now commonly followed in this 
country, and to some extent in Europe, and the 



Testing Tensile Strength. 43 

method given by the Association of German Ce- 
ment Makers, which is more commonly emploN^ed 
in Europe. 

The American Method as recommended by the 
committee is as follows : "The proportions of 
cement, sand and water should be carefull3^ de- 
termined by weight, the sand and cement mixed 
dry and the water added all at once. The mixing 
must be rapid and thorough, and the mortar, 
which should be stiff and plastic, should be firmly 
pressed into the molds with a trowel, without 
ramming, and struck off level ; the molds in each 
instance while being charged and manipulated 
to be laid directly on glass, slate or .some other 
non- absorbent material. 

The molding must be completed before incipient 
setting begins. As soon as the briquettes are hard 
enough to bear it, they should be taken from the 
molds and be kept covered with a damp cloth un- 
til they are immersed. For the sake of unifor- 
mity, the briquettes, both of neat cement and those 
containing sand, should be immersed in water at 
the end of 24 liours, except in the case of one- 
day tests." 

' ' The proportion of water required varies with 
the fineness, age or other conditions of the ce- 
ment, and the temperature of the air, but is ap- 
proximately as follows : 



44 Hydraulic Cement, 

For briquettes of neat cement : Portland about 
25%, Natural about 30%. 

For briquettess of i part cement, i part sand : 
about 15% of total weight of sand and cement. 

For briquettes of i part cement, 3 parts sand : 
about 12% of total weight of sand and cement. 

The object is to produce the plasticity of rather 
stiff plasterer's mortar." 

By the German method the mortar is mixed 
more dry than in the above and the mold is filled 
heaped with it ; it is then rammed into place and 
pounded until the mortar grows elastic and the 
water flushes to the surface, after which the bri- 
quette is struck off level, and, as soon as it is hard 
enough, taken from the mold and treated as in the 
other case. 

The French standard specifications require the 
mortar to be plastic and placed in the mold with- 
out ramming, but the side of the mold may be 
lightly tapped with the trowel to disengage the 
air bubbles that may remain in the mortar. This 
tapping of the mold is quite efficient in settling 
the mortar into place, and tends to give uniform- 
ity to the briquettes. 

There are two points to be especially noted in 
making briquettes by hand : first, the mortar 
must be very thoroughly worked in mixing, both 
the French and German rules require that it shall 
be briskly mixed for five minutes, sufficient mor- 



Testing Tensile Strength. 45 

tar being prepared at once for 5 or 6 briquettes ; 
second, the air bubbles must be well worked out 
of the mortar in filling the molds. The neglect 
of these precautions causes much of the irregu- 
larity which commonly exists in the work of in- 
experienced operators. With more experienced 
men there exist differences in the amount of 
working, the pressure given in placing in the 
molds and the quantity of water used, which 
cause wide variations in results. 

Mechanical Appliaiices for Making Briquettes. — 
In order to reduce the effect of the personality of 
the operator in making tensile tests of cement, 
various appliances for mixing and molding bri- 
quettes by machinery have been tried. 

For mixing, an apparatus arranged to shake 
the materials rapidly up and down, on the prin- 
ciple of the ordinary milk shake, has been ap- 
plied in a number of places, but usually without 
satisfactory results. 

The mixing apparatus of Mr. Faija, with 
w^hich good results are reported to have been ob- 
tained, consists of a cylindrical pan, in which a 
mixer, formed of four blades, revolves both on its 
own axis and about that of the pan. The writer 
has had good success in the use of a very simi- 
lar apparatus, consisting of a closed brass cylin- 
der, in which the mixer, composed of verti- 
cal rods held by a horizontal arm, revolves 



46 Hydraulic Cement. 

about the axis of the cylinder and also about the 
middle point of the arm. By the use of such an 
apparatus the mortar may be thoroughly mixed 
much more expeditiously than by hand, and with 
greater uniformity. 

For molding the briquettes, the apparatus which 
has been most frequently applied is the Bohme 
hammer, which consists of an arrangement by 
which 150 blows are struck by a hammer of 2 kil- 
ograms weight upon a plunger, sliding in a guide 
mold, placed over the mold in which the briquette 
is to be formed. A high degree of density is 
thus produced in the briquette, and the air is 
thoroughly expelled. More regular results are 
thus obtained, depending much less upon the 
personality of the operator, than by the ordi- 
nary method. The objection to the use of this 
method is the slow and tedious nature of the 
work. 

A more satisfactory method of molding is by 
the use of a single application of a direct steady 
pressure. An apparatus for this purpose devised 
by Professor Jamieson of the University of Iowa 
has given satisfactory results, and has been intro- 
duced in a number of places. In this apparatus, 
appliances are also provided for the rapid feeding 
of the mortar to the mold and the immediate re- 
moval of the briquette from the mold. 

It has been found by the writer that a pressure 



Testing Tensile Strength. 47 

of about 500 lbs upon the surface of the briquette 
is sufficient to produce a compact and homogene- 
ous briquette, and a crude appliance, consisting 
of a lever arranged to bring a pressure upon the 
mortar in the mold by means of a weight sus- 
pended at the end of the lever, has been found to 
increase both the rapidity and the regularity of 
the work, and especially to diminish the varia- 
tions in results obtained by different men. 

Greater uniformity in tensile tests of cement is 
highly desirable and it seems possible to reach it 
only by the application of automatic appliances 
in making the briquettes. If a standard pressure 
could be agreed upon, a simple and inexpensive 
apparatus for molding briquettes could be readily 
applied anywhere, and, coupled with some form 
of mechanical mixer, would do much toward cor- 
recting the irregularities that now exist. 

Qua7itity of water used in mixing. — The rules 
recommended by the committee of the American 
Society of Civil Engineers require that the mor- 
tar used in making briquettes should be stiff and 
plastic. The German rules, under which the 
molding is done by pounding the mortar in the 
molds, require that the mortar should be mixed 
quite dry. In each case the water used depends 
largely upon what idea the man doing the work 
may have regarding what is meant by the terms 
used in describing the process, and in practice a 



48 Hydraulic Cement, 

very considerable variation will be found in this 
regard in the work of different men. 

The French rules for standard tests, which are 
very similar in the method of making briquettes 
to those recommended by the committee of the 
American Society of Civil Engineers, give the 
following methods of determining if the mortar 
be of proper consistency : 

ist. The consistency of the mortar should not 
change sensibly if the mixing be continued three 
minutes after the expiration of the required five 
minutes. 

2nd. If a small quantity of the mortar be taken 
up on the trowel and allowed to fall upon the 
mixing slab from a height of 50 centimeters, it 
should be detached from the trowel without leav- 
ing any small particles adhering, and, after fall- 
ing, should approximately retain its form without 
cracking. 

3rd. A small quantity taken in the hand and 
patted into a round form, until water is brought 
to the surface, should not stick to the hand, and, 
when allowed to fall from a height of one-half 
meter, the ball should retain its rounded form 
without showing any cracks. 

To meet these requirements leaves but a narrow 
limit within which the consistency may vary. If 
a slightly too small quantity of water be used, the 
mortar would crack upon falling. If the quan- 



Testing Tensile Strength. 49 

tity be very slightly too great, the mortar will 
continue to soften upon further working, will be 
sticky, and will lose its form upon falling. 

When the briquettes are molded by a machine, 
the quantity of water will necessarily be less than 
in hand work, and when using pressure the quan- 
tity may be regulated by making it all that the ce- 
ment will take without having it squeezed out un- 
der the pressure. This will leave the briquette 
sufficiently firm to be immediately removed from 
the mold without injury. 

Form of briquette. — Many forms of briquettes 
have been tried, but at the present time there are 
but two in common use : the one recommended 
by the committee of the American Society of 
Civil Engineers, which was originally UvSed by 
Mr. Faija in England and is now standard in this 
country and commonly used in England ; the 
other is the one adopted by the Association of 
German Cement Makers and is the standard in 
France and Germany. 

The principal difference in these forms is that 
in the American form the section diminishes grad- 
ually from the end to the middle, while in the 
German form the area is decreased suddenly by a 
circular notch at the middle. Comparative tests 
of briquettes of the two forms, having the same 
section, show that the English form will give 
higher results in nearly all cases than the Ger- 



50 Hydraulic Cement. 

man, the difference being usually 30 to 40 per 
cent, of the smaller. This may be accounted for 
by the fact, stated by Mr. Faija, that a sudden 
change of cross section is always an element of 
weakness. 

In this country and in England, the standard 
minimum section of the tensile briquette is one 
square inch, in Germany and France it is five 
square centimeters. 

The use of this small section is advantageous, 
both because it admits of using lighter apparatus 
in making the tests and because greater uniform- 
ity is attainable in preparing the small briquette. 
The strength obtained is greater per unit of area 
than would be had with larger vSpecimens, and of 
course the strength by standard tests is much 
greater than can be developed by the material in 
actual use. 

The size of the breaking section has an impor- 
tant effect upon resulting strength, the smaller 
the section, the higher the strength per unit of 
area. 

M. Durand-Claye has shown that the strength 
varies with the perimeter of the section rather 
than its area, and that the interior may be re- 
moved leaving only a shell, without diminishing 
the strength. 

Applying the Stress. — In order to produce uni- 
form results in tensile tests, it is necessary that 



Testing Te7isile Strength, 51 

the stress shall be so applied as always to bring a 
direct tension upon the small section of the bri- 
quette, and also that the rate of application of the 
stress shall be uniformly the same. The rate of 
application commonly adopted is about 400 lbs. 
per minute. The machines in common use some- 
times regulate this by causing the stress to be 
brought upon the briquette by the flow of a small 
stream of water or shot into a bucket suspended 
from the lever of the testing machine. This is 
highly satisfactory as giving uniformit}^ of result, 
although there is a small impact due to the fall 
of the shot into the bucket, which may slightly 
affect the absolute measurement of the stress. In 
order that the stress upon the briquette shall be 
axial, care must be exercised in properly center- 
ing the briquette in the clip, and the form of the 
clip must be such that it shall not clamp or bind 
upon the head of the briquette, but may be free to 
adjust itself to an even bearing. The surface of 
contact between the briquette and clip must be 
large enough to prevent the material of the bri- 
quette being crushed at the point of contact, and 
as small as possible to permit of its more free 
self-adjustment. The suspension of the clips, as 
is usual, by conical bearings permits of their 
turning so as to transmit the stress in a right line 
between bearings. 

Various devices have been proposed for the ac- 



52 Hydraulic Cement, 

curate centering of briquettes and to permit the 
more free adjustment of the clip to the direction 
of stress. In general, however, these do not seem 
necessary aud are of little practical value. The 
use of a rubber bearing between the clip and 
briquette, as devised by Mr. Cock, is vSaid to 
produce satisfactory results, in facilitating the ad- 
justment of the line of stress, and in the elimina- 
tion of cross stresses and irregular breaks in the 
test pieces. 

Sand Test. — Sand tests, although commonl}^ 
recommended, are not very generally used in or- 
dinary specifications, where reliance is usuall}^ 
placed upon the neat test, coupled with that for 
fineness, to indicate what the cement will do when 
mixed with sand. A tensile test with sand is, 
however, undoubtedly of the greatest value when 
properly conducted, as according more nearly with 
the conditions under which the cement is to be 
used than does the neat test. 

In making briquettes for sand tests, it is of first 
importance that the cement and sand be very 
thoroughly mixed before the addition of the water. 

The nature and degree of fineness of the sand 
has a very large influence upon the strength 
of the mortar. For standard tests in this countr}^ 
an artificial sand, made by crushing quartz, is 
used. The size of standard sand is such that it 
will pass through a sieve of 400 meshes per square 



Testing Te7isile Strength. 53 

inch, and be caught upon one of 900 meshes per 
square inch. Tests are also sometimes made with 
the sand which is to be used in the work, although 
this is rarely done. 

Te7isile Streiigth Required. — As has already 
been stated, the tensile strength developed by ce- 
ment on a short time test is no necessary indica- 
tion of the strength that may be attained by it 
during a longer period, unless the normal action 
of the particular material be known. That which 
is the strongest at first will not necessarily con- 
tinue the strongest. 

Mr. Faija recommends that the gain in strength 
between the 7 and 28 day periods be considered, 
rather than the absolute early strength, in deter- 
mining the probable vSubsequent gain in strength. 
This is probably a better guide than the usual one, 
but it is not ordinarily practicable to require a test 
extending over a period of 28 days, and even were 
it pOvSsible, it would in many cases be misleading. 

Professor Unwin gives a formula for the 
strength at any period, y=^a-\-b{^x — i)"", in which 
y is the strength required at x weeks after mix- 
ing, a the strength at the end of one week, n a 
constant for the particular material to be deter- 
mined by observation extending over consider- 
able time, and b a constant to be determined from 
the strengths given by the sample at i and 4 
weeks after mixing. Professor Unwin gives the 



54 Hydraulic Cement, 

value n^=-yz for Portland cement in general, and 
shows that the formula gives values according 
well with the results of tests in many instances. 
This formula, as will be readily seen, depends 
upon the assumption that for any two Portland 
cements the gains in vStrength at end of any 
period are to each other, as the gains between 
the 7 and 28 day tests, a proposition which for 
many Portland cements will scarcely hold, al- 
though approximately true for a considerable 
class of materials. 

To make this method of practical use, it would 
be necessary to determine a formula for each kind 
or brand of cement. 

It should be observed that some cements which 
quite closely follow the curve indicated by the 
formula, early reach their full strength, and 
make a quite abrupt break at the point which 
seems to mark the completion of the process of 
hardening, thus necessitating the use of an upper 
limit to the value of x, varying for different 
material. 

Whatever may be the rate of subsequent hard- 
ening, the early tensile strength, when dealing 
with a material whose characteristics are known, 
is, without doubt, a very efficient help in the esti- 
mation of the value of a sample. 

The strengths commonly required by specifi- 
cations in this country are based upon the recom- 



Testing Tensile Strength, 55 

mendatioiis of the American Society of Civil 
Engineers, which are as follows : 

^'American Natural Cement, Neat : 

I day, I hour or until vSet in air, the rest of the 
24 hours in water, from 40 to 80 pounds. 

I week, I day in air, 6 days in water, from 60 
to 100 pounds. 

I month, I day in air, 27 days in water, from 
100 to 150 pounds. 

I year, i day in air, remainder in water, from 
300 to 400 pounds, 

American and Foreign Portland Cements^ Neat : 

I day, I hour or until set in air, the rest of the 
24 hours in water, from 100 to 140 pounds. 

I week, I day in air, 6 days in water, from 250 
to 550 pounds. 

I month, I day in air, 27 days in water, from 
350 to 700 pounds. 

I year, i day in air, remainder in water, from 
450 to 800 pounds. 

American Natural Cements, i part Cement to i part of 

Sand: 

I week, I day in air, 6 days in water, from 30 
to 50 pounds. 

I month, I day in air, 27 days in water, from 
50 to 80 pounds. 

I year, i day in air, remainder in water, from 
200 to 300 pounds. 



56 Hydraulic Cement, 

American and Foreign Portland Cements^ i part of 
Cement to 3 parts of Sand : 

I week, I day in air, 6 days in water, from 80 
to 125 pounds. 

I month, I day in air, 27 days in water, from 
100 to 250 pounds. 

I year, i day in air, remainder in water, from 
200 to 350 pounds.'^ 

At least the minimum values here given for i 
and 7 days are usually required in ordinary speci- 
fications. These values, however, need modifi- 
cation according to the kind of cement used, 
especially with the natural cements, which vary 
so widely in character. The requirements for 
each cement should depend upon what is known 
of it. Thus, natural cements from the Hudson, 
from the Potomac or from the Ohio, would need 
quite different specifications to insure good qual- 
ity in each case. 

The specifications, especially on large works 
where permanent laboratories are maintained, re- 
quire modifications also according to the practice 
of the laboratories. 

The results of tests in these laboratories is 
usually to give a higher strength for the same 
material than would be obtained on an ordinary 
outside test, especially by a comparatively inex- 
perienced man. I^ack of skill in conducting the 
test always tells against the material tested. 



Tests fo r So ic n dji ess. 57 

while the extraordinarily high values, given out 
as obtained for some cements by certain of these 
fixed laboratories, are probably due more to 
skillful manipulation of the test than to differ- 
ences in the material. 

ART. 14. TKSTS FOR SOUNDNESS. 

Soundness is the most important quality of a 
cement, as it means the power of the cement to 
resist the disintegrating influences of the atmos- 
phere or water in which it may be placed. Un- 
soundness in cement may vary greatly in degree, 
and show itself quite differently in different ma- 
terial. Cements in which the unsoundness is 
very pronounced are apt to become distorted and 
cracked after a few days, when small cakes are 
placed in water. Those in which the disinte- 
grating action is slower may not show any visible 
change of form, but after weeks or months, even, 
may gradually lose coherence and soften until en- 
tirely disintegrated. 

The method in common use for testing un- 
soundness is to make small cakes or pats of neat 
cement, usually about 3 or 4 inches in diameter 
and ^2 inch thick, upon a plate of glass, and 
keep them in air or water for a few days, care- 
fully watching them to see if they show any 
signs of distortion or surface cracks, which may 
indicate a tendency to disintegration. 



58 Hydraulic Cement. 

The German standard specifications require 
that the cakes for this test shall be 1.5 centime- 
ters thick at the center and have thin edges. 
These cakes are placed under water 24 hours after 
they are made, or at least not until they are 
firmly set, and observations are continued over a 
period of 28 days, when, if no crack or distortions 
appear, the cement is considered sound. 

The method recommended by the committee of 
the American Society of Civil Engineers is to 
make two cakes or pats as for the German tests 
and observe them as follows : 

"One of thCvSe cakes, when hard enough, 
should be put in water and examined from day 
to day to see if it becomes contorted, or if cracks 
show themselves at the edges, such contortions or 
cracks indicating that the cement is unfit for use 
at that time. In some cases the tendency to 
crack, if due to free lime, will disappear with 
age. The remaining cake should be kept in the 
air and its color observed, which for a good ce- 
ment should be uniform throughout, yellowish 
blotches indicating a poor quality ; the Portland 
cements being of a bluish gray and the natural 
cements being light or dark, according to the 
character of the rock of which they are made. 
The color of the cements when left in the air in- 
dicates the quality much better than when they 
are put in water. " 



Tests for Soundness. 59 

The color test above given is not considered to 
be of much value, as unsound cements are very 
commonly of good color. 

The time during which these observations shall 
continue is not specified in these rules, but in 
practice they are not usually carried over more 
than from two days to a week before acceptance 
of the material. 

It is important in testing soundness in this 
manner that the tests should be continued for as 
long a period as possible, and many cavSes of un- 
soundness will not be discovered even with a 28 
day test. Cases have been observed in which 
mortar, in the form of 2 inch cubes, has com- 
pletely disintegrated within two 3^ears, where in- 
cipient checking was not observable for three 
months in a small cake test. The most common 
and dangerous cases of unsoundness are probably 
discovered by the ordinary tests. It may be 
observed, however, that the fact, that cases of 
disintegrating mortar are not oftener observed in 
large constructions, is probably due more to the 
general good quality of the cement supplied by 
the best makers, and to the frequent stability of 
work regardless of the nature of the mortar, than 
to the efficiency of the test for soundness. 

The quantity of water to be used in mixing 
cakes for these tests is about the same as that 
used for tensile tests, although a variation in the 



6o Hydraulic Cement. 

quantity does not seem to appreciably affect the 
result. Care should be taken in making these 
tests, that the cakes be kept in moist air during 
the setting and previous to immersion, in order 
that they may be free from drying cracks, which 
would not indicate any imperfection in the 
material. 

ART. 15. ACCKlyKRATED TESTS FOR SOUNDNKvSS. 

The fact, that many cases of unsoundness in 
cement are not discoverable by the ordinary vShort 
time tests, is well known, and consequently 
several tests, intended to show more conclusively 
the value of the cement, have been proposed. 

Most of these tests are based upon the idea of 
the advancement of the process of disintegration 
by the action of heat, and vSome of them have 
proven satisfaotory in use, although none of them 
have been extensively used in practice. 

Hot tests were first suggested by Dr. Michaelis, 
who proposed to use heat for the advancement of 
hardening of the cement, claiming that cements 
kept in hot water would in a short time gain the 
full strength to be attained during a long time in 
cold water. This, while true of a certain class of 
cements, proved to be untrue of a large number 
of others of somewhat different composition. 
Subsequently Professor Le Chatelier proposed to 
modify the test, by advancing the idea that the 



Tests for Soiuidiiess. 6i 

gain in strength in hot water over that in cold 
water was an indication of the soundness of 
the cement, and suggesting the testing of 
briquettes of i to 3 mortar kept hot and cold, 
and accepting as sound that in which the 
strength of those kept hot is as great or greater 
than that of those kept cold, at the end of a few 
days. 

Of this it may be said, as of the first proposi- 
tion, that there are many cases in which it is un- 
true, some flagrantly unsound cements gaining 
strength very rapidly in hot as compared with 
what they will attain in cold water. 

A few of the tests now proposed and used in 
different places are given below. 

Kiln Test. This test, originaied by Dr. 
Bohme, is included in the standard German 
specifications for cement which is to be used in 
the air. Under those specifications, cement to be 
used under water is also subjected to this test, but 
its result in this case is not considered decisive, 
the conclusive result being that of the 28 day 
cold water test, as given in Art. 14. 

To make the kiln test, cakes of neat cement, 
made as for the ordinary cold test, after 24 hours in 
moist air, are placed in a drying oven and ex- 
posed to a temperature of 110° to 120° centigrade 
for at least an hour or until no more water 
escapes. If after this treatment the cakes show 



62 Hydraulic Ce7nent. 

no edge cracks, the cement is to be considered 
sound. In some cases this test is prolonged to 
3 or 4 hours, and sometimes the heat is applied 
gradually. 

This test is considered of value in Europe for 
use with cements to be used in air. It has never 
been used in this country to any extent. Cement 
to be used in water should be subjected to a wet 
test. 

Steam and Hot Water Test. This test consists 
in subjecting cakes of cement, prepared in the 
ordinary manner, to the action of steam for 3 or 4 
hours, then immersing in hot water for the re- 
mainder of 24 hours, and examining for cracks 
and distortions. 

Mr. Faija, by whom this test was devised, UvSes 
it in his specifications for cement in England. 
Mr. Faija describes his method of conducting the 
test as follows. 

''Briefly, it is a vessel containing water, the 
water being maintained at an even temperature 
of about 110° to 115° Fahr. ; there is a cover to 
the vessel, so that above the water there is a 
moist atmosphere which has a temperature of 
about 100° Fahr. The manner of carrying out 
the test is by making a pat, in the manner already 
described, on a small piece of glass ; immediately 
the pat is gauged it is placed on a rack in the 
upper part of the vessel and is there acted upon 



Tests for Soundness. 63 

by the warm vapor rising from the hot water, 
when the pat is set quite hard it is taken off the 
rack and put bodily into the water, which, as has 
been already stated, is maintained at a temper- 
ature of 110° to 115° Fahr., and in the course of 
24 hours it is taken out and examined, and if 
found then to be quite hard and firmly attached 
to the glass, the cement may at once be pro- 
nounced sound and perfectly safe to use ; if, how- 
ever, the pat has come off the glass and shows 
cracks or friability on the edges, or is much 
curved on the under side, it may at once be de- 
cided that the cement in its present condition is 
not fit for use." 

Mr. Faija prefers the temperature given above, 
but other experimenters have seemed to get better 
results using a higher one. Prof. Tetmajer ob- 
tained fairly good results with a temperature just 
below the boiling point, about 200° Fahr , and 
.subjected the cakes to the action of steam 4 hours, 
and hot water 20 hours, placing the cakes in the 
steam as soon as mixed. 

Mr. Maclay has modified this method of test- 
ing, and introduced it into the specifications of 
the Department of Docks of New York Cit}^ 
Four pats or cakes of cement made in the usual 
manner are used by Mr. Maclay for his tests, the 
conduct of which he describes as follows. 

'' One of these pats is placed in a steam bath, 



64 Hydraulic Cement. 

temperature 195° to 200° Fahr., as soon as it is 
made. The second pat is placed in the same 
steam bath as soon as it is set hard, and can bear 
the I pound wire. The third pat is placed in the 
steam bath after double the interval has elapsed 
that it took the pats to set hard, counting from 
the time of gauging. The fourth pat is placed in 
the steam bath at the end of 24 hours. 

*' The first four pats are each kept in the steam 
bath 3 hours, then immersed in water of a temper- 
ature of about 200° Fahr. for 21 hours each, when 
they are taken out and examined. To pass this 
test perfectly, all four pats, after being 21 hours 
in hot water, should upon examination show no 
swelling, cracks nor distortions, and should ad- 
here to the glass plates. The latter requirements, 
while it obtains with some cements nearly free 
from uncombined lime, is not insisted upon, the 
cracking, swelling and distortion of the pats being 
much the more important features of this test." 

When only the first pat fails Mr. Maclay does 
not reject the cement but allows it the advantage 
of being set before being submitted to the steam. 
This lessens the severity of the test, and is a 
matter of judgment as to the degree of unsound- 
ness that may be allowable. 

Mr. Maclay also subjects those samples which 
fail upon this test to a second one before rejecting 
them, by testing the tensile strengths of briquettes 



Tests for Soundness. 65 

kept in hot water and comparing them with those 
kept cold. If the hot strength is greater than 
that cold, he deems the cement normal in compo- 
sition but perhaps underburned. The tCvSts are 
made upon briquettes 2, 3, 4, and 7 days old, of i to 
2 mortar. This is practicall}^ the method first 
suggested by Prof. Le Ch atelier, already alluded 
to, and its use in this manner is recommended by 
M. Candlot, who states that cements of proper 
composition, slightly underburned, and capable of 
giving good results in use, may fail on the hot 
cake test, but will give good results in the hot 
strength test, when in a mortar containing sand. 

The wisdom of thus qualifying the results of 
the steam and hot water test seems very question- 
able. As stated, at the beginning of this article, 
the action of heat to promote the hardening of 
mortar varies greatly with cement of slightly dif- 
ferent compositions, and some of the worst qf un- 
sound cements show most satisfactory strengths 
in hot water. 

Boiling Test. — This test consists in mixing cakes 
in the usual manner, placing them at once in cold 
water, raising the temperature of the water to boil- 
ing in about an hour, continuing boiling for three 
hours, and then examining for checking and soft- 
ening. Its use is recommended by Prof. Tet- 
majer as the result of an extended series of ex- 
periments, including the use of the other hot tests, 



66 Hydraulic Cement. 

and observations of the material tested over long 
time under normal conditions. 

This test is the most severe of those proposed, 
and may, as is sometimes claimed, reject certain 
underburned cements of good composition, but, in 
general, there seems to be no difficulty in the 
meeting of its requirements upon the part of good 
cements, either Portland or natural, although it is 
questionable whether certain light burned natural 
cements of the magnesian variety should be sub- 
jected to it. 

If the cement be allowed to set before putting 
the cakes in the water, this test becomes practi- 
cally the same as the steam and hot water test. 

Professor Tetmajer recommends for this, and in 
fact for all pat tests, that the cakes shall not be 
made with thin edges. His method of making 
the pats is to roll a ball of the cement mortar, 
and flatten the ball to the required thickness. 
The mortar must be of such consistency as that 
it shall not crack in flattening, and shall not run 
at the edges. For the hot tests this method 
seems desirable, but in the slower cold tests still 
longer time would be required to obtain results 
than by the ordinary method. 

Chloride of Calcium Test, This test is suggested 
by M. Candlot, and is designed to detect the 
presence of free lime or sulphate of lime in ap- 
preciable quantities. 



Tests for Soundness. 67 

The writer has found it to give true indications 
in a number of cases, including some unsound 
magnesian cements. It consists in mixing the mor- 
tar for the cakes, with a solution of 40 grammes 
chloride of calcium to i litre of water, allowing 
them to set, immersing them in the same solution 
for 24 hours, and then examining them for check- 
ing and softening as in the other tests. 

There has been much discussion of late regard- 
ing these accelerated tests, and considerable op- 
position has been developed to their use in 
specifications, although in certain cases they have 
been so used. It has been definitely shown that, 
in general, certain of these tests do detect un- 
soundness in cement, where it can not be detected 
by the ordinary method. It has also been shown 
that good cements will usually pass them. It is 
possible that for different makes of cement there 
would be a variation in results for these, as there 
is for the other tests which are applied, but the 
reasonable presumption is against the soundness 
of any cement that fails upon nearly any of 
these tests when properly made. 

Further experiments are desirable to determine 
the actual connection between the results of tests, 
and the action of the material during a long time 
under normal conditions. 

When the action of these tests upon the differ- 
ent cements is more fully known, the tests may 



68 Hydraulic Cement, 

be adapted to the material at hand so as to attain 
the best results. Until that time, however, it is 
reasonable, upon all important work, to apply 
such tests as will insure the good quality of the 
material used, even at the risk of rejecting other 
good material. 

ART. l6. CHEMICAI, ANAI.YSIS. 

Chemical tests are not commonly made for the 
purpose of determining the quality of cement, 
and are only of limited value for that purpose, 
in so far as the user is concerned. The value of 
cement depends not only upon its being com- 
posed of the proper relative quantities of the dif- 
ferent ingredients, but also upon the state of com- 
bination of those ingredients, which in turn de- 
pends largely upon the care used in manufactur- 
ing the cement. 

The soundness of the cement cannot in general 
be shown by analysis unless it contains too great 
quantities of substances which are known to be 
injurious, as for instance, a considerable percent- 
age of sulphuric acid, or of magnesia, in Port- 
land cement. The existence of free lime can not 
be shown by analysis, except as it may be in- 
ferred from a knowledge of the normal hydraulic 
index of the material. 

Under the French standard specifications, any 
Portland cement is rejected which contains more 



Compressive Tests, 69 

than 1% of sulphuric acid, or sulphides in ap- 
preciable quantity, while those with more than 
4% of oxide of iron, or with a hydraulic index 
less than -^W, are regarded with suspicion. Sim- 
ilar requirements are imposed in some other Euro- 
pean countries. 

M. Candlot states that a chemical analysis may 
be useful in showing the adulteration of cement, 
sometimes practiced in Europe. Upon sifting 
the cement and separately analysing the coarse 
and fine portions, an unadulterated cement 
should show practically identical results for the 
two analyses. He also states that blast furnace 
slag, which is a common adulteration in Portland 
cement, may sometimes be discovered by the 
odor of sulphuretted hydrogen upon treating it 
with hydrocloric acid. 

ART. 17. COMPRESSIVE TESTS. 

The compressive strength of cement mortar is 
very much greater than its tensile or adhesive 
strength, and as it does not seem to give any 
better indication of value, while much more diffi- 
cult of determination than the tensile strength, 
it is not usually employed as a test of quality. 
The compressive strength of mortar is commonly 
stated to be about 10 times its tensile strength al- 
though there is of course a considerable variation 
in the actual ratio. 



70 Hydraulic Cement, 

In making compressive tests, cubes of 2 inch 
sides are generally used, these are moulded and 
treated in the same manner as the briquettes for 
tensile tests, and in breaking are commonly 
placed between the heads of the testing machine, 
with a thin layer of plaster of paris between the 
plate of the machine and the surface of the bri- 
quette, to bring it to an even bearing, and dis- 
tribute the pressure uniformly. 

The strength obtained upon a compressive test 
will vary with the size of the specimen used, the 
largest block giving the highest strength, and 
also as in the tensile test with the method of pre- 
paring the specimen. In Kurope, standard test 
pieces for compressive tests are always moulded by 
the use of the hammer. 

It may be noted that the compressive test dif- 
fers from that for tension, in that the strength of 
the material of the whole block must be over- 
come to produce rupture, instead of that of the 
surface only, and that the compressive resistance 
in practice where the mortar is used in larger 
masses, will probably be greater than that of the 
test pieces. 

Compressive tests are sometimes made, and 
are of great value, for the purpose of determining 
the strength actually developed in the work, 
under various contingencies of use. 



Adhesive Tests. 71 

ART. 18. ADHESIVE TESTS. 

Adhesive tests are not commonly employed in 
determining the value of cement, because of the 
uncertain nature of the test, and the difficulty of 
so conducting it as to make it a reliable indica- 
tion of value. Adhesive power is, of course, a 
very important characteristic of a cement, but an 
indication of this is obtained when the sand test is 
used, or when the neat tensile strength is coupled 
with a test for fineness. 

It is to be observed that the adhesive strength 
is not necessarily proportional to that of cohesion, 
even when the fineness is the same, and that dif- 
ferent varieties of cement may possess the prop- 
erty of adhesion in quite different degrees. The 
sand test, however, calls into play, to a certain 
extent, the adhesive power, and is at least a par- 
tial measure of adhesive strength. 

Adhesive strength is developed much more 
stowly than cohesive, and the difference between 
the two, while very considerable on short time 
tests, may be gradually lessened with time. This 
may be seen illustrated in the fact that a cement 
which, when gauged neat, attains its full strength 
in a few weeks, may, when mixed with sand, 
continue to gain in strength for a year, and 
finally develop as much strengih as in the first 
case. 



72 Hydraulic Cement. 

Experiments for the purpose of determining 
the adhesion of mortar to various substances are 
very desirable, in order to extend knowledge of 
the material in this most important, but little 
known, property. 

The best method of conducting this test is 
probably to make briquettes, of which one-half 
shall be of cement of the ordinary form for ten- 
sion, and the other half a piece of stone, glass or 
whatever surface is to be used, of the same sec- 
tion as the mold, at its middle, and arranged so 
that it may be caught in the clips of the testing 
machine at the other end. This may be accom- 
plished by filling out with cement or plaster if 
necessary, or a special clamp may be used in 
place of the clip for catching a rectangular block 
at one end of the briquette, which must be left 
free to adjust itself to an axial stress. 

ART . 19. MICROSCOPIC TKSTS. 

Tests for cement by miscroscopic examination 
have been proposed, and some observations made 
for the purpose of determining whether any idea 
of the quality of the cement could be obtained 
from such examination, with varying results. 
While it is unlikely that such a test will come 
into general use for determinations of value, it is 
quite probable that much may thus be learned 
concerning the nature and action of the material. 



Abrasion Tests. 73 

There are two methods by which such work 
may be carried out ; first, by cutting sections of 
unground cement rock, or of briquettes made of 
the cement, and examining its constitution in the 
ordinary method for rock ; and second, by ex- 
amining the cement powder under the microscope, 
and noting the character of the grains of which 
it is composed. 

With cements of the Portland class, it has 
been observed that the active portion of the 
cement is composed of grains of angular form 
and metallic lustre, and that the portions having 
an earthy appearance are probably inert. It has 
also been found that the color of the grains seem 
to bear some relation to their value in the 
material, although this has not been investigated 
sujSiciently to state any general deductions. 

Professor Le Chatelier by his study of sections 
of unground Portland cement rock has added 
very greatly to the knowledge of the constitution 
of Portland cement ; much however remains to be 
done in this direction. 

ART. 20. ABRASION TESTS. 

In Germany tests of the resistance of cement 
blocks to abrasion are frequently employed, es- 
pecially where the material is to be subjected to 
wear in use, as in walks. 

For this purpose the apparatus of Prof. Baus- 



74 Hydraulic Cemefit. 

chinger is commonly employed. This apparatus 
consists essentially of a cast iron rotating disk 
upon which the specimen is held, with constant 
pressure, by a weight at the end of a lever. A 
certain amount of sand is used to assist the grind- 
ing action, and after a given number of turns the 
loss of weight of the specimen is determined. 
Thus the comparative value of various cements 
to resist wear, as well as of various mixtures of 
cement and sand are determined. 

It has been found that mortars containing small 
proportions of sand resist wear better than those 
of neat cement. 

ART. 21. AIR SIvAKING. 

Sometimes fresh cement, when first opened after 
being shipped, will, if tested, show an abnor- 
mally rapid rate of setting, and subsequently 
harden very slowly, so that on short time tests 
very low teUvSile strength will be given. If, how- 
ever, this cement be exposed to the air for a few^ 
days, it may resume its natural rate of setting, 
and attain proper strength upon the tests. In 
some laboratories it is customary to thus expose 
cement to the air a short time before testing, and 
this process is termed air slaking. 

The propriety of air slacking in testing cement 
is questioned by some engineers, upon the ground 
that the cement to be used in the work will not 



Air Slaking. 75 

be treated in the same manner. In England, it 
is customary to give such exposure to all cement 
to be used upon important work for at least ten 
days, but in this country the cement is commonly 
used just as received from the manufacturer. 

The general practice seems to be in favor of 
air slaking the cement in testing it, and it seems 
probable that a cement capable of regaining its 
normal condition in a few days will not endanger 
the work, even if used at once, but it would 
doubtless be better in using such cement, to air 
slake the whole of it before using. 

In many cases the strength after three or six 
months will be as great, when it is mixed before, 
as when after air-slaking, although the difference 
of strength on a test extending over a few days 
is very considerable. 

If the cement blows or shows unsoundness on 
the first test, the propriety of using it in the 
work, without first exposing it to the air, is more 
doubtful, even though this point be also regained 
on the second test. 



CHAPTER. III. 

THK USK OF CKMKNT. 



ART. 22. SAND FOR MORTAR. 

As hydraulic cement is nearly always mixed 
with certain proportions of sand, when used in 
construction, the nature and quantity of sand used, 
and the method of manipulating the materials in 
forming the mortar have an effect nearly as im- 
portant upon the final strength of the work as 
the quality of cement itself. 

In testing cement, as has been stated in art 13, 
an artificial sand, made b}^ crushing quartz, is 
commonly employed. This sand may be had quite 
uniform in quality. In the execution of work, 
however, natural sand from the locality must gen- 
erally be used ; this will vary widely in its nature, 
and should always be carefully considered upon 
any important work where the development of 
strength and lasting qualities in the mortar is of 
importance. 

A sand for use in mortar should be as clean 
and free from loam, mud or organic matter as 
possible. A small admixture of pure clay may 
not be objectionable, and has been shown in some 
instances not to decrease the strength, when pres- 
ent to an extent not exceeding ten per cent, of 



Sand f 07' Mortar. 77 

the sand. But, in general, the presence of any 
foreign matter in the sand is to be avoided, and 
M. Alexandre has shown that clay, in mortar to 
be used in sea water, may be an element of danger, 
acting like unsound cement to cause disintegration. 

The sand should also be as sharp as possible; 
if it be composed of angular grains, it will com- 
pact much closer and make a much stronger 
mortar, when used with the same proportion of 
cement, than if it be composed of rounded grains. 

Uniformity of size of grain is also desirable 
when the mortar contains a considerable propor- 
tion of sand. 

Coarse sand is preferable to that which is very 
fine, giving better strength to the mortar, 
especially in the case of mortar rich in cement. 
Fine sand may, however, be desirable when an 
impervious mortar is the object. 

In using a quick setting cement the dryness of 
the sand is a matter of importance, as, if the sand 
be damp, when the mixture of sand and cement 
is made, sufficient moisture may be given off to 
the cement to induce a partial setting previous to 
the addition of the water. With slow setting 
cement this is of less consequence. 

The proportion of sand to cement to be used in 
any case, depends upon the nature of the work and 
the necessity for the development of strength or im- 
perviousness in the mortar. The relative quanti- 



78 Hydraulic Cement. 

ties of sand and cement should also depend upon 
the nature of the sand, although this element is 
not usually considered. 

The proportions most commonly used in 
ordinary work are, for natural cements, one part of 
cement to one part of sand, or in vSome cases, one 
part of cement to two parts of sand, and for Port- 
land cement, one part of cement, to three parts 
of sand. If the proportions of the mixture were 
regulated by the value of the sand, the interests 
of econony might frequently require changes in 
proportions and would generally demand the use 
of the best sand obtainable A good sand mixed 
in a I to 3 mortar will frequently give better 
strength than a poorer sand mixed in the propor- 
tion of I to 2, and either mortar give equally good 
results in practice. 

It is not, of course, practicable to use these 
materials with any certainty as to the absolute 
strength that is being attained in the work, but 
a test of the sand used, under the actual condi- 
tions of use, might often contribute largely to our 
knowledge of the result that is being produced. 
The best way to value the sand for use is by test- 
ing it in comparison with the standard testing 
sand, and many natural building sands will show 
results as to strength of mortar equal or superior 
to that sand. 



Water for Mortar. 79 

ART. 23. WATKR FOR MORTAR. 

The quantity of water to be used in mixing 
mortar can be determined only by experiment in 
each case. It depends upon the nature of the 
cement, upon that of the sand and of the water, 
and upon the proportion of sand to cement. 

Fine sand requires more water than coarse sand 
to give the same consistency, and the mortar with 
fine sand should be made a little more wet than 
with coarse sand to give the best results in the 
work. Dry sand will take more water than that 
which is moist, and sand composed of porous 
material more than that which is hard. As the 
proportion of sand to cement is increased, pro- 
portion of water to cement should also increase, 
but in a much less ratio. Less sea water than 
fresh will be required to produce a given con- 
vSistency. 

The amount of water to be used in mixing 
mortar for ordinary masonry is such that the mor- 
tar when thoroughly mixed shall have a stiff 
plastic consistency. 

It should not be a soft, semi-fluid mass. The 
required consistency is described by M. Candlot* 
as such that if a ball of mortar be formed in the 
hand and allowed to fall through a small height, 



* Ciment et Cliaux Hydraulique, E. Candlot, Paris, 1891. 



8o Hydraulic Cement. 

it should neither lose its form nor crack ; the ball 
should not be wet enough to stick to the hand. 

The greatest cohesive strength will be given by 
mixing as dry as possible, while the adhesive 
strength will be greater in a wet mixture. The 
best results are obtained in practice by mixing 
the mortar with as little water as will admit of its 
proper manipulation and thoroughly wetting the 
surface to which it is to adhere. 

In all cases the proper quantity of water should 
first be determined by experiment upon small 
quantities of the materials, and afterward, in 
preparing the mortar for use in the work, the re- 
quired quantity should each time be added b}^ 
measurement. The addition of the water little 
by little, or from a hose, vShould never be allowed. 

ART. 24. MIXING MORTAR. 

In mixing cement mortar, the cement and sand 
are first thoroughly mixed dry, the water then 
added and the whole worked to a uniformly plas- 
tic condition. 

The value of the mortar will depend upon the 
thoroughness of the operation ; the cement must 
be uniformly distributed through the sand during 
the dry mixing, and thoroughly working the 
mass after the addition of the water will greatly 
increase its strength. 

In mixing by hand, by the ordinary method, a 



Mixing Mortar. 8i 

platform or box is used ; the sand and cement 
are placed upon the platform in layers, with a 
layer of sand at bottom, and then turned and 
mixed with shovels until properly distributed 
through the mass. The material is then formed 
into a ring, or into a mound with a crater at the 
center, and all the water necessary added at once 
being placed in the center, after which the ma- 
terial is thrown up from the sides until the water 
is all taken up, and is then worked into a plastic 
condition. 

In order to secure proper manipulation of the 
materials, on the part of the workmen, it is quite 
common to require that the whole mass shall be 
turned over a certain number of times with the 
shovels, both dry and wet. 

The mixing should be quickly and energeti- 
cally done, only such quantity being mixed at 
once as can be used before the initial set of the 
mortar takes place. 

The cement should not be left in contact with 
the sand for any considerable time before being 
used, or a considerable quantity should not be 
mixed dry and left to stand until wanted, as the 
moisture, usually in the sand, will, to some extent, 
act upon the cement. 

Upon large works, mechanical mixers are fre- 
quently employed with the advantage of at once 
lessening the labor of manipulating the material 



82 Hydraulic Cement. 

and insuring good work. There are a number of 
forms of mixers which do thorough and satisfac- 
tory work. 

ART. 25. CONCRETE. 

Concrete is usually formed of a mixture of 
broken stone, or gravel, with sufficient cement 
mortar to bind the mass firmly together. The 
stone used should be as hard and durable as pos- 
sible, and that of angular form and uniform size 
will give better results than if it be rounded and 
uneven. Angular forms give a greater vSurface 
for the adherence of the mortar in proportion to 
the volume, while leaving a less volume of inter- 
stices to be filled by the mortar. The amount of 
sand used should be such as will just fill the 
voids in the stone, while the quantity of cement 
will depend upon the strength necessary to de- 
velop for the particular work under consideration. 

When the concrete is required to be water 
tight, the amount of cement must be sufficient to 
fill the interstices in the aggregate composed of 
the combined sand and stone. 

The amount of sand necessary to fill the inter- 
stices in the stone may be determined by filling a 
measure with stone, as closely as possible, and 
then measuring the quantity of water which can 
be poured into the measure ; this will give the 
volume of sand required. If the proper quantity 



Concrete. 83 

of damp sand be added to the stone in the meas- 
ure by shaking it down so as to fill the voids, the 
volume of water which can then be put into the 
measure will be the volume of cement necessary 
to fill the voids in the aggregate. 

The strength of the concrete will usually vary 
nearly in proportion to the amount of cement 
used in forming it. When a strong concrete is 
desired, it should be obtained by increasing the 
richness of the mortar in cement, not by increas- 
ing the proportion of mortar to large material 
above the point where the sand fills the interstices 
in that material. If the proportion of sand be 
less than this, the resulting concrete will be por- 
ous and not thoroughly solidfied ; if it be greater, 
the excess of sand will be an element of weak- 
ness in the concrete. 

In the use of concrete in considerable masses, 
the main body of the work is vSometimes formed 
of a very weak concrete, with a facing of stronger 
watertight concrete to protect it. This weak con- 
crete is frequently formed by omitting the sand 
altogether, and simply coating the stone lightly 
with neat cement mortar, causing the stones to ad- 
here to each other, thus forming a mass suffi- 
ciently firm for foundations in many locations 
when protected by a covering of richer concrete. 
The voids in a mass of ordinary broken stone 
vary from about y% to -f^ of the volume, depend- 



84 Hydraulic Ceme?it. 

ing upon uniformity of size. The proportions in 
common use for concrete of Portland cement vary 
from I part cement, 2 parts sand, and 5 parts 
broken stone to i part cement, 4 parts sand and 8 
or 10 parts broken stone or gravel. Usually the 
mortar is made somewhat richer when natural 
cement is to be used. The proportions, of course 
must vary with the character of the materials to 
be used, as well as that of the work to be done, 
and can only be properly determined by the ex- 
ercise of good judgment in the light of expe- 
rience. 

In preparing concrete, the mortar is mixed in 
the usual manner, then the stone is spread over 
the top of the layer of mortar and thoroughly 
mixed with it by turning with shovels. The 
stone should be vSprinkled sufficiently to wet its 
surface before being mixed with the mortar, in 
order to prevent the absorption of the water from 
the mortar, and to promote the adherence of the 
mortar to the stone. 

The mortar for concrete should never, as is 
quite commonly done, be reduced to a fluid state ; 
not only will the mortar be weakened by so doing, 
but it cannot be properly mixed with the stone to 
form a homogeneous mass, as the cement will 
wash out of the mixture. 

Mechanical mixers are frequently employed for 
preparing concrete, and are very useful in the 



Mix hires of Lime and Cement, 85 

saving of labor especially where considerable 
quantities are being used. 

Concrete should always be used immediately 
after mixing, and should not be disturbed after 
the initial set of the cement. It will also be 
benefitted by being well rammed into place. 

ART. 26. MIXTURES OF I.IME AND CEMENT. 

Common .slaked lime is frequently mixed with 
Portland, or natural cement for the purpose of 
decreasing the cost of construction. In works 
to be exposed mainly to the air, experiment seems 
to indicate that a very considerable percentage of 
lime may sometimes be added without material 
loss of strength in the mortar. 

For mortar to be used under water, the loss of 
strength is greater when lime is mixed with the 
cement, and the propriety of its use is more ques- 
tionable. 

Experiments in this matter have not been suffi- 
ciently extended to admit of any general deduc- 
tions. The question of the advisability of such 
mixture in any case is mainly an economic one, 
and turns upon the determination of whether it 
be cheaper to form a certain volume of mortar of 
given strength by the use of the mixed lime and 
cement, or by the use of the cement alone with 
more sand. 



86 Hydraulic Cement. 

The admixture of lime causes the cement to 
become slower setting, affecting the quick setting 
cements more strongly than the less active ones. 
In damp situations the durability of the mixture 
is also open to question. 

In France, a small percentage of Portland ce- 
ment is sometimes added to hydraulic lime, with 
the effect, it is claimed, of considerably augment- 
ing the strength and also of accelerating the set- 
ting of the lime. 

Mixtures of natural with Portland cements 
have frequently been used in this country, and 
seem, in general, to give a result which is a mean 
of the properties of the cements mixed. In all 
of these cases, in order to obtain good results the 
mixture must be very intimate. 

ART. 27. FRKKZING OF MORTAR. 

Mortar of good Portland, or of many kinds of 
natural cement, is not injured in strength by 
freezing, even if it be frozen before it is set. The 
cement will not set while frozen, but, if allowed 
to thaw out, will afterward set. 

The hardening of cement which has been 
frozen will be much more slow than if unfrozen, 
but it may ultimately gain the same strength. 

Masonry constructed in freezing weather will 
frequently be injured by freezing, notwithstand- 
ing the fact that the cement itself shows no loss 



Freezing of Mortar. 87 

of strength due to freezing. The effect of frost 
coming upon the work before it is fully hardened 
is frequentiy to distort or cause unequal settle- 
ment in it, and sometimes repeated freezing and 
thawing gradually causes the mortar to force out 
and crack off, or perhaps disintegrate on the out- 
side. The construction of cement masonry dur- 
ing freezing weather is therefore, generally, more 
or less hazardous, unless some means be taken to 
prevent the freezing action. Many instances 
may, however, be cited, where extreme cold has 
not injured work constructed, without such pre- 
caution, with Portland cement mortar, and it is 
claimed by many engineers that Portland cement 
may be UvSed with impunity in freezing weather, 
but usually it is not placed in the work while a 
freezing temperature prevails. It is commonly 
agreed that most natural cements should not be 
used when a very low temperature is likely to 
reach the work in advance of its having attained 
good strength, and instances are numerous where 
work has been injured by the changing tempera- 
tures of winter weather, although it may have 
been constructed several weeks before being 
frozen. 

Salt is very commonly used in cold weather to 
prevent the freezing of the mortar while it is soft. 
A strong solution, frequently a saturated one, is 
employed. The salt, by preventing the freezing 



88 Hydraulic Cement. 

of the water, prevents any distorting or disrupt- 
ing action upon the work due to the change in 
volume of the mortar. The salt has, of course, 
no eflFect to prevent injury to the cement in any 
case in which a loss of strength would result from 
a low temperature without its use. 

The use of salt in mortar considerably decreases 
the activity of the cement, and mortar will not 
usually set at freezing temperatures, even if salt 
be used to prevent freezing, or at least, the setting 
action at low temperatures is so slow as to be im- 
perceptible during several days. Usually no in- 
jury will be done the mortar by standing in a soft 
condition at freezing temperatures as the volume 
will not change, it can not dry out, and when a 
sufficient temperature is reached it will set, but 
much more slowly than if it had not been ex- 
posed to the low temperature. 

The decrease of early strength in cement mor- 
tar, which has been mixed with salt water, when 
exposed to a low temperature, is usually greater 
than that of mortar of the same cement mixed 
without the salt and frozen at the same tempera- 
ture. - 

The effect of salt upon the strength of various 
kinds of cement is quite different. In nearly all, 
the strength of mortar kept in the air is increased 
by its use. When the mortar is kept in water, 
most cements will have an access of early strength 



Freezing of Mortar. 89 

from the use of salt, which will later be lost, the 
final strength being somewhat reduced. This is 
true of nearh^ all Portland cements Some natur- 
al cements suffer a material loss of strength when 
mixed with salt water, while others are entirely 
ruined b}^ a low temperature with or without the 
admixture of salt. In general, however, the 
natural cements derive more benefit than Port- 
lands from the use of salt. Care should always 
be taken to determine the action of salt and cold 
upon the particular cement before applying it in 
use. 

Care should be taken in using salt, that af- 
ter the mortar has been subjected to a freezing 
temperature it does not come into contact with 
water for a considerable time, as mortar contain- 
ing salt, after it has warmed up and set, will fre- 
quently be softened and disintegrated by the ac- 
tion of water, unless sufficient time has elapsed 
to admit of its hardening sufficiently to resist such 
action. 

Soda is sometimes employed to prevent the 
freezing of mortar, but its use has not become 
extensive. 

Hot water should not be used in mixing mortar 
in freezing weather, as it not only decreases the 
strength of the mortar, but renders it more liable 
to injury from frost. Heating the stones or bricks 
in the construction of masonry in freezing weath- 



90 Hydraulic Cement. 

er may be beneficial, as serving to accelerate the 
setting and keep the cement from freezing while 
soft. 

The injury done to mortar by freezing, howev- 
er, is probably not usually due to freezing before 
setting, but to alternate thawing and freezing 
while the work is still fresh, and before harden- 
ing is sufficiently advanced to be capable of ade- 
quately resisting the disrupting forces. The effect 
of frost upon mortar which has set is similar to 
that upon vStone or brick, and is due to the in- 
crease of volume of the water which freezes in 
the pores of the mortar. Its effect, therefore, de- 
pends both upon the porosity of the mortar and 
upon the strength it possesses to resist disruption. 
The more rapid acquisition of strength by the 
Portland cements may give them the advantage 
they usually possess in this regard. 

ART. 28. POROSITY AND PERMKABII^ITY OF MORTARS. 

The permeability of cement mortars varies with 
the quality of the cement and the circumstances 
of its use. Mortar of neat Portland cement may 
be made practically impermeable under a consid- 
erable head of water ; that composed of cement 
and sand seems always more or less permeable, 
but when properly proportioned and mixed will 
eventually permit very little water to pass under 
small heads. 



Porosity and Per?neabilzty of Mortars. 91 

The permeability of mortar decreases rapidly 
with Its age ; for the first few days or weeks after 
mixing water passes quite freely through it, but 
as the hardening process approaches completion 
its power of resistance is, in this particular, great- 
ly augmented. 

Both the porosity and permeability are less for 
mortar rich in cement than for that in which the 
proportion of cement is small. Mortar mixed dry 
is penetrated more readily than that mixed to a 
plastic or semi- wet condition. The thoroughness 
of mixing and degree of compacting employed 
are, however, more important factors than the ab- 
solute quantity of water used in mixing. 

Fine sand, according to the experiments of M. 
Alexander, renders the mortar more porous and 
less permeable than coarse sand. When the sand 
is of varying sizes, both the porosity and perme- 
ability may be low. In any case, to attain a rea- 
sonable resistance to penetration, it is necessary 
that the interstices in the sand be entirely filled 
with cement. Cleanliness of the sand, and its 
freedom from all foreign material, is of first im- 
portance in the preparation of impermeable mor- 
tar. 

Masonry of ordinary brick or stone can only be 
made impervious by the application of a coating 
of some kind to its face. A plastering of neat 
cement or of rich mortar may frequently be used 



92 Hydraulic Cement. 

for this purpose and coatings of asphaltum or 
coal tar have sometimes been successfully em- 
ployed. 

In concrete work where imperviousness is 
essential it is advisable, as with masonry, to coat 
the face of the concrete. In order that concrete 
may be made reasonably watertight, it is neces- 
sary that the quantity of cement mortar used in 
preparing it be sufficient to fill the voids in the 
large material employed, as well as, that the 
voids of the sand be completely filled with 
cement in making the mortar. 

ART. 29. EXPANSION AND CONTRACTION OF MORTAR. 

In the use of large masses of masonry, or con- 
crete, the change that is liable to occur in the 
volume of mortar may frequently become of im- 
portance, and it may be necessary to make pro- 
vison by which change of dimension can take 
place without injury to the work. 

The coefficient of expansion of neat cement 
mortar, under the action of heat, is, as already 
stated, approximately the came as that of iron, 
although there may be a considerable variation 
in some cases. For mortar containing sand the 
coefficient is less than for neat cement. 

Cements differ considerably in their behavior 
during the continuance of the hardening process, 



Expa7isio7i and Contraction of Mortar. 93 

as to the change that takes place in the volume 
of the mortar. Unsound cements are apt to 
swell and become distorted at the commencement 
of the process of disintegration, and, of course, 
any considerable change of this nature indicates 
the probable destruction of the mortar. Perfectly 
sound cement, although not altered in form, is 
usually changed somewhat in dimensions during 
hardening ; if the mortar be kept in dry air, a 
slight shrinkage takes place ; if under water, the 
mortar vSwells a little. 

Professor Swain, in a "series of experiments 
made at the Massachusetts Institute of Technol- 
ogy for a committee of the American Society of 
Civil Engineers, found that, for small blocks of 
mortar, the change was the same in all directions ; 
that for neat cements, the linear contraction in 
air varied from 0.14% to 0.32% for the first 12 
weeks after mixing, and the linear expansion in 
water varied from 0.04% to 0.25%. When sand 
was used the change was less, giving a contrac- 
tion in air of from 0.08% to 0.17% and an ex- 
pansion in water of from 0.00% to 0.08%. 

The rapidity of the change in volume varies 
also, to some extent, with the activity of the 
cement ; the conclusion being that a quick 
setting cement changes more in volume than a 
slow setting one. 

Further experiment upon this point is desirable 



94 Hydraulic CeTuent, 

in order that the action of the various classes of 
cements may be better understood. 

ART. 30. EFFKCT OF RETEMPERING MORTAR. 

Masons very frequently mix mortar in con- 
siderable quantities, and, if the mass becomes 
stiffened, before being used, by the setting of the 
cement, add more water and work again to a soft or 
plastic condition. After the second tempering, 
the cement is much less active than at first and 
will remain for a longer time in a workable con- 
dition. 

This practice is now very generally condemned 
by engineers and is not usually allowed in good 
engineering construction, although there is con- 
siderable dispute as to the injurious effect of re- 
tempering upon the mortar. M. Alexander, from 
a large series of experiments concerning this mat- 
ter, concludes that no injury is usually done to 
the mortar by retempering it. provided sufficient 
water be added to make the material plastic at 
the second working. The hardening of mortar 
so treated is at first very slow, and it gives very 
low early strength, but it may subsequently (the 
tests extend over 3 years ) gain as much strength 
as when gauged immediately upon mixing. 

Other experimenters have seemed to show that 
in some cases injury is done to mortar by retem- 



Effect of Re tempering Mortar. 95 

pering, some cement even refusing to set the 
second time. In the light of our present knowl- 
edge, therefore, it seems advisable to mix only 
such quantity at once as may be used before the 
initial set of the cement, and to reject any mate- 
rial that may have become set before being placed 
in the work. 



CHAPTKR IV. 

LITERATURK RKIvATiNG TO CKMKNT. 



ART. 31. I.IST OF PERIOD! CAI, I^ITKRATURK. 

The following list of literature, relating to hy- 
draulic cement, has been arranged for the purpose 
of aiding students in making special study of the 
subject. Only such papers have been included 
as seem to possess some definite value for purposes 
of research. The list is, for the most part, limited 
to works which may be found in the Cornell Uni- 
versity Library, and is far from complete, but in- 
cludes many of the more important recent contri- 
butions to the knowledge of the subject. 

PAPERS IN KNGI^ISH. 

1. AivKXANDRK, Paui^. — Porosity and Permeability of 

cement morters and their decomposition by sea water. 
Engineering News^ Jan. 10, i8gi. 

2. ARN01.D, H. — Effect of sand upon the strength of 

Cement. Eng. News, July 11, i88j. 

3. Bakkr. I. O. — Economy in the composition of cement 

mortar. Eng. News, March 10, 1888. 

4. Bamber, H. K. — Portland Cement, its manufacture, 

use and testing. Proc. Institution Civ. Eng., Vol. 
107, p. 31. .... 

5. BeckwiI'h, Arthur. — The Composition of Ancient 

Cement and Rosendale Cement. Trans. Am. Soc. 
C. E., Vol. II, p. 171. Also Van No strand' s Mag,, 
Vol. 8, p. 20s. 

6. Bernays, E. a. — Portland Cement Concrete. Proc. 

Institution Civil Engineers, Vol, LXII, p. 87. 



List of Periodical Literature. 97 

7. BoswKiyiv, St. GkorGK. — The Quebec Harbor Improve- 

ments. Trans. Canadian Sac. C. E., Vol. i, part 2, 

P' 77- 

8. Brown, A. H. — Microscopic Tests for Cements. E^ig. 

News, Nov. 21^ i8gi. 

9. Bruner, p. M. — Effect of low temperatures on Port- 

land cement concrete. Jour. Assoc. Eng. Soc, Vol. 
7, P' 125. 

10. Burnett, S. F. — Selection, Inspection and Use of 
Cements. Jour. Assoc. Eng. Soc, Vol. 7, p. 2^8. 
Also R. R. Gazette, v. 20, p. y^^. 

11. Buti^er, M. J. — The Manufacture of Natural Cements, 

Trans. Canadian Soc. C E., Vol. IV, p. 95. 

12. Carey, A. B. — The testing of Portland Cement for 
Public Works. Froc. Inst. Civil Eng., Vol. loy, p. 
40. 

13. Chibas, B. J.— Cost of Concrete and Masonry. En- 
gineering Record, Apr. 11, i8gi. 

14. C1.ARK, E. C. — Record of Tests of Cement made for 
Boston Drainage Works. Trans. Am. Soc. C. E., 

Vol. XIV, p. 1 4. 1. 

15. Cock, W. R. — Letters describing rubber bearing for 
clips. Engineering News, Jan. 77, i8gi, and Dec. 
22, i8g2. 

16. CoivSON, Chari^es. — Experiments on the Portland 
Cement used in the Portsmouth Dockyard Extension 
Works. Proc. Inst. C E., Vol. XLI, p. 125. 

17. DeSmedt, E. J.— New York Dock Department Ce- 
ment Tests. A letter in Eng. News, Dec. 5, i8gi. 

18. DeSmedt, E. J.— Chemical Tests for Cement. Let- 
ters in Eng. News, Dec. 26, 188^, Jan. 2j, and Feb. 
IS, 1886. 

19. Durand-CIvAYE and Debray. — Permeability of Ce- 
ment Mortar. (See paper No. III.) Jour. Franklin 
Inst., March, i88g ; also Eng. Record. Nov. 2j, i88g. 

20. EngIvER. — Cement, Hydraulic lyime, Roman Cement, 
Portland Cement. Eng. News, Feb. 7 and Feb. 14, 
i8gi. 

21. Faija, Henry. — On the Mechanical Examination 
and Testing of Portland Cement. Proc. Inst. C. E., 

^ol. 75, p. 213. 



98 Hydraulic Cement. 

22. Faija, Henry. — Portland Cement. Trans. Society 
of Engineers^ June, 188^. 

23. Faija, Henry. — Portland Cement Testing. Trans. 
Am. Soc. C. E., Vol. 17, p. 218. 

24. Faija, Henry. — On the Manufacture and Testing of 
Portland Cement. Paper before Engineers^ Con- 
gress, Chicago, i8g3 

25. FerET, R. — Mortar for Sea Works. Engineering, 
July 28, 1893. 

/26. Francis, J. B. — High Walls or Dams to Resist the 
Pressure of Water. Tfans. Am. Soc. C. E., Vol. ig, 
p, 147. 

27. Freeman, H. C— Cement Works of the Utica Ce- 
ment Co. Trans. Am. Inst. Mining Eng., Vol. ij, 
p. 172. 

28. Friswei.Iv, R. J. — Manufacture of Slag Cement. 
Eng. Record, Nov.- 12, 1887. 

29. Gary, Max. — The Testing of Portland Cement and 
the Development of the Cement Industry in Ger- 
many. Paper before Engineers' Congress, Chicago, 

1893- 

30. Grant, John. — Experiment upon the Strength of 
Portland Cement. Proc. Inst. C. E., Vol. 32, p. 266. 

31. Grant, John. — Portland Cement, its Nature, Tests 
and Uses. Proc. Inst. C. E., Vol. 62, p. 98. 

32. Grant, Wm. H. — Notes on Cement, Mortars and 
Concretes. Trans. Am. Soc C. E., Vol. 2^, p. 2^9. 

33. Hyde and Smith. — Permeability of Cement Mortar. 
Jour. Franklin Inst., Sept., 1889. 

34. KiNiPPivE, W. R. — Concrete Work Under Water. 
Proc. Inst. C E., Vol, 87, p. 6^ ; also abstract in Eng. 
Record, Feb. 21, 1891. 

35. KuiCHiviNG, E. — Cement Mortar for Public .Works. 
Eng. Record, March 24. and 31, Apr. 14. and 21, 1888. 

36. Larned, W. F. — Mixing and Handling Concrete at 
Boston Water Works. Eng. News, Dec. 24, 1887. 

37. IvE CHATE1.IER, H. — The Composition of Cement 
Under the Microscope. (From paper 121.) The 
Builder, Vol. 42, p. 701. 

38. IvE ChateIvIER, H. — Tests of Hydraulic Materials. 
Paper before Engineers' Congress^ Chicago, 1893. 



List of Periodical Literature. 99 

39. Leslie. R. W. — Letter Concerning a New Form of 
Cement Specification. E7ig. News, Aug. 22^ i8gi. 

40. LowcocK, S. R. — Strengtli of Concrete Slabs. Free. 
Insiitutio7i. C. E., Vol. iii, p. Jj2 ; also Lng. Xezi'S, 
MsLy /, /Sgj. 

41. LuxDiE, John. — Concrete. Jour. Assoc. E7ig. Soc. 

Vol. 6, p. 437. 

42. Maclay, \V. W. — Notes and Experiments on the Use 
and Testing of Portland Cement. Ti'a^is. Am. Soc. 
C. E.. Vol. VL p. 311, with discussion in Vol. VII, 
p. 280. 

43. Maclay, V\'. \V. — Hot Tests for determining change 
of volume in Portland Cement. Traits. Am. Soc. 
C. E., Vol. 2 J. p. 4.12. 

44. Manx. I. J. — The Adhesive Strength of Portland Ce- 
ment. Proc. Pist. Civ. E7ig., Vol. 7/, p. 412. Also 
Van Nostra7id' s Mag., Vol. 2g, p. 233. 

45. Manx'. I. J. — TheTestingof Portland Cement. Proc. 
Pist. Civ. E7ig., Vol. 47, p. 248. 

46. Massy. G. H. — Foundations of the St. Lawrence 
Bridge. Trans. Canadia7i Soc. C. E.. Vol. i.p.36. 

47. Messent, p. J. — Concrete in Sea Water. London 
Engineeri7ig, Jan. 27, 1888. 

48. MiCHAELis. — The Manufacture and Use of Portland 
Cement. Va7i Xostra7tds Mag., Vol. i,p. 746. 

49. MiCHAELis, W. — The behavior of Portland Cement in 
Sea Water. Pi'oc. hist. Civ. Eng., J^ol. 107, p. 371. 

50. Miller, T. D. — The Louisville Cements. Jour. 
Assoc. E7ig. Soc. . Vol. 5, p. 187. 

51. MuRPHY', M. — Concrete as a substitute for Masonr}- 
^ in Bridge Work. Trans. Canadia7i, Soc. C. E., Vol. 

2. p. 79. 

52. Murphy. M. — Bridge Substructure in Nova Scotia. 
Paper before Engineers' Congress, Chicago. ^^93- 

53. Newkirch, Fr. — 'Improved method of constructing 
Foundations under water by forcing cement into 
loose sand or gravel. Paper hejore Engi7ieers^ Con- 
gress, Chicago, i8g3. 

53a. Noble, Alfred. — Effect of Freezing upon Mortar. 
T7'a7is. A771. Soc. C. E., Vol. 16, p. 79. 



loo • Hydraulic Cement. 

54. NoBivE, Ai^FRKD. — Bxperiments with appliances for 
Testing Cements. Trans. Am. Soc. C. E., Vol. p, 
p. 186. 

55. Norton, F. O. — American Natural Cements. Trans. 
Am. Soc. C. E., Vol. p, p. 280. 

56. Parsons, H. De B. — The Influence of Sugar upon 
Cement. Trans. Am. Soc. Mechanical Eng., Vol. 
9, p. 286. 

57. Powers, M. I.--The Effect of Salt upon Cement 
Mortars. Eng. News, Nov. 21, 1801. 

58. Prime, F. — The Cement Works on the Lehigh. Sec- 
ond Geol. Surv. of Penn'a, i8j6, Vol. DD. 

59. Ransome, F. — Improvements in Manufacture of 
Portland Cement. The Builder, Sept. 17, i88j. 

60. Redgrave, G. R.— Slag Cement. Proc. Inst. C. E., 

Vol. CV, p. 21^. Abstract in Eng. and Min. Jour., 
May 2^, 1 8 go. 

61. RusSEivL, S. Bent. — Neat Test vs. Sand Tests for 
Portland Cements. Trans. Am,, Soc. C. E., Vol. 2^, 

/. 295- 

62. RUSSELI., S. B. — The Cement Laboratory of the St. 
Louis Water Works Bxtension. Eng. News, Jan. j, 
1891. 

63. Sabin, L. C. — Variation in Cement Testing Sieves. 
Eng. News,Juue30, i8g2. 

64. Schermerhorn. — Concrete Breakwaters. Eng. 
News, Jan. ji, i8gi. Eng. Record, May 16, i8gi. 

65. Scott and Redgrave. — The Manufacture and Test- 
ing of Portland Cement. Proc. Inst. C, E. , Vol. 62, 
p. 67. 

66. S1.ATER, John. — Concrete. The Builder, March 20, 
1882. 

67. Smith, W. — Influence of Sea Water on Portland 
Cement. Proc. Inst. Civ. Eng., Vol. 107, p. 73. 

68. SoNDERiCKER, J. — Investigation as to how to Test 
the Strength of Cements. Jour. Assoc. Eng. Soc, 
Vol. 7, p. 207. 

69. Spai^ding, F. p. — Accelerated Tests for Permanence 
of Volume of Cement Mortars. Eng. News, Aug. 
24, i8q3. 

70. Unwin, W. C. — On the Rate of Hardening of Cement 
and Mortar. Proc. Inst. C. E., Vol. 84, p. jgg. 



List of Periodical Literature . loi 

71. WhiTTEMORR, D. J. — Tensile Tests of Cement, and 
an Appliance for More Accurate Determinations. 
Trans. Am. Soc. C. E., Vol. g, p. j^p. 

72. Ward, W. B. — Beton Combined with Iron in Build- 
ings. Trans. Anier. Soc. Mech. Eng., Vol. IV, p. 
388. 

73. Weber, C. O. — The Practical Application of Magne- 
sia Cement. (See paper No. 157.) Scien. Am. Sup., 
May 16, i8gi. 

74. YardIvEY, B. — Bxperiments on Cement. Trans. 
Am. Soc. C. E.. Vol. 2, p. 153. 

75. GoDDARD and Bvans. — Bffect of Retempering Ce- 
ment Mortars. E^ig. News, Jan. 5, 18^3. 

76. McCuivEOCH, W. — Construction of a Watertight Ma- 
sonry Dam. Trans, Am. Soc. C. E., March, 18^3. 

VARIOUS NOTES, REVIEWS AND REPORTS. 

77. Adulterated Cement Question in Germany. The 
Builder, Vol. 42, p. 'joi. 

78. Anti-freezing Soda Mortar. Eng. News, Feb. 16, 

1893- 

79. Concrete for Harbor Work. Proc. Inst. C\ E., Vol. 
87, p. 92. 

80. Concrete in Sea Water. R. R. Gazette, Vol. 19, p. 

570. 

81. Concrete Plant at the Cascades Canal, Oregon. Eng. 
News, June 2, 1892. 

82. Concrete in Harbor Work. Lon. Engineering, Oct. 
7, 1892. 

83. Failure of Concrete Piers. En%. News, Dec. 11, 1886. 

84. The Hardening of Hydraulic Cement. Engineer, 
Lojidon, Sept. 21, 1888. 

85. German Specifications for Standard Portland Cement. 
Eng. News, Nov. 13, 1886. 

86. Influence of Sea Water on Portland Cement. Eng. 
Record, Dec. 26, 1891. 

87. Influence of Sugar upon Cement. Eng. News, Dec. 
24, 1887. 

88. Monier Method of Constructing Arches. Eng. News, 
May 23, 1 89 1. 

89. Manufacture of Portland Cement from Slag. Scien- 

tific American Sup., May 31, 1890. 



I02 Hydraulic Cement. 

90. Novel English Portland Cement Plant. Eng. News, 
March 21, i8gi. 

91. Overburnt Cement. Lon, Eftgineer, Dec. 2, i8g2. 

92. Portland Cement as a Structural Material. Engineer- 
ing Record, Dec. 79, i8gi. 

93. Porta Cement Works at Bremen. Lon. Eng'ng, 
July //, i8gi. 

94. Report of the Committee on a Uniform System for 
Tests of Cement. Trans. Am. Soc. C. E., Vol. 14, 

P' 475- 

95. Report of Progress of Committee on the Compression 
of Mortars and Settlement of Masonry. Trans. Am. 
Soc. C. E., Vol. //, p. 21 J. 

96. Resolutions of the Conferences at Munich and Dres- 
den concerning Uniform Methods of Testing Materi- 
als. Trans. Am. Soc. Mech. Eng., Vol. 11, p. jjj. 

97. Tensile Strength of Beton. Eng. News, May //, 
i8go. 

98. Strange Behavior of Cement. Eng. News, Nov. 26, 
i88j, also Dec. ly, 1887. 

PAPERS IN FRKNCH 

99. Ai^KXANDRK, PauIv. — Experiences concernantl'influ- 
ence du dosage de I'eau sur le resistance des mortiers 
de ciment. Annales des Fonts et Chaussees, 1888, 
Vol. I, p. 375. 

100. Ai^EXANDRK, Paul. — Recherches Experimentales 
sur les mortiers hydrauliques. An. Fonts et Chaus., 
i8go. Vol. II, p. 277. 

loi. Barrkau. — Les qualites et essais des ciments a prise 
leute. An. des Fonts et Chaussees, 1882, Vol. 11, p. 
150. 

102. BoNNAMi, H. — Etude relative a I'influence de I'alu- 
mine sur la resistance des ciments de Portland. 
Genie Civil, Vol. 14, p. 180. 

103. Briji,!,, a. — Etude sur les qualities du ciment de 
Portland. Annales des la constr^iction, 1881, col 1^0. 

104. Candi^ot, E. — Note contenant les resultats d'expe- 
riences faites sur le ciment de Portland gache au 
chlorure de calcium. Annales de la construction^ 
1886, col 171. 



List of Periodical Literature. 103 

105. Candlot, B. — Note sur I'emploi des materiaux hy- 
drauliques. A7inales de la Co7istruction, i88g. 

106. Candlot, E. — Note sur la prise et le durcissenient 
des mortiers de cimeut de Portland. A71. de la Con.^ 
1888. 

107. Devai,. — Essais a I'eau cliaude des ciments et chaux 
hydrauliques. Annates Industrielles, i8go, Vol. 2, 
p. 408. (See also paper No. 137.) 

108. DoivOT. — Note sur Taction du gypse sur les mortiers. 
An. de la Construction, 1888, col. ii^. 

109. DuRAND - CivAYE^ AND Dkbray. — Etude sur les ci- 
ments Magnesiens. An. des Fonts et Chaussees, 1886, 

Vol. /, p. 845. 
no. DuRAND-CivAYK AND Debray. — La dilatation des 
pates de ciment de Portland. An. des Fonts et 
Chaiissees, 1888, Vol. /, p. 810. 

111. DuRAND-CivAYK AND Dkbray. — PermeabiHte des 
mortiers de ciments Portland. An. des Fonts et 
Chans., 1888, Vol. r,p. 816. (See paper No. 19.) 

112. Feret, R. — Diverses Experiences concernant' les 
ciments. An. des Fonts et Chaussies, i8go, Vol. /, 

P' 3^3- 

113. FerET, R. — Sur la compacite des mortiers hydrau- 
liques. An. des Fonts et Chaussees, i8g2, Vol. 2, p. 5. 

1 14. FoY, T. — Etude sur les ciments de Laitier. Annates 
Indiistrielles, 1887, Vol. 2, p. 724. 

115. FoY, J. — Etude sur les ciments siliceux. Annates 
Fidustrielles, 1888, Vol. 2, p. 814. 

116. GroscIvAUDE, J. — Etude sur la fabrication et les 
proprietes du ciment de laitier. Annates Industri- 
elles, i88g, Vol. 2, p. 89. 

117. GoBiN, A. — Fabrication des cbaux hydrauliques. 
A71. des Fonts^ et Chaussees, i88j, Vol. 2, p. 464. 

118. GoBiN, A — Etude sur les ciments de I'lsere. An. 
des Fonts et Chaussees, i88g, Vol. i, p. y^^. 

119. Lechartier. — Influence de la magnesie dans les 
ciments dits de Portland. An. de la Construction, 
1886. 

120. LeChaTEIvIER, H.— Recherches experimentelles sur 
la constitution des Ciments. A?tnales des Fonts et 
Chaussees, 1882, Vol. i, p. 482. 



I04 Hydraulic Cement. 

121. LkChaTKIvIKR, H. — Recherches experimentelles 
sur la constitution des Mortiers hydrauliques. An- 
nales des Mines, iSSy, Vol. /, p. ^4-5- (See paper No. 

-37-) 

122. PkrrodiIv. — Surlamarche du durcissement des Mor- 
tiers. An. des Fonts et Chausees, 1884., Vol. /, p. S92. 

123. Prost, M. a. — Iva fabrication et les proprietes des 
ciments de laitier. Annates des Mines, i88g, Vol. 2^ 

124. ViCAT. — Etude sur la pouzzolane. An. des Po?its et 
Chaussies, i8j6, Vol. 2, p. g6. 

125. ViCAT. — Ponzzolanes artificielles. An. des Fonts et 
Chaus. , 1842, Fart 2, p. /jj. 

126. Vic AT. — Influence de I'eau de mer sur les Mortiers 
de pouzzolane artificielle. An. des Fonts et Chaus. ^ 
1843, p. 232. 

127. ViCAT. — Mortiers a la mer. An. des Fonts et Chaus., 
1834, Vol. 2, p. 8. 

PAPKRS IN GERMAN. 

128. Bauschinger, J. — Verhandlungen der Miinchener 
conferenz und von ihr Gewahlten Standigen Commis- 
sion zur Vereinbarung einheitlicher Priifungsmeth- 
oden fur Ban- und Constructions-Materielen. Mit- 
theilingen aus dem Mechanisch- Technischen Labora- 
torium, Munich, No. 16. 

129. BOHM.— -Ueber das System Monier. Civil inge- 
nieur, i8gi, p 4'/4. 

BoHME. — Mittheilungen aus de^n K. technischen 
Versuchsaustalten , Berlin . 

130. 1883, p. j8. — Ueber den Kinfluss der Zusatz von ver- 
schiedenen pulverformigen Substanzen auf Portland- 
Cemente. 

131. 1883, p. g3. — Untersuchung der cemente auf Voluni- 
bestandigkeit nach verschiedenen Methoden. 

132. 1886, p. 30. — Kinfluss des Frostes bei mit Schlacken- 
zusatz versehenen Portland-Cementen. 

133. 188^, p. 108. Ueber die abnutzbarkeit der Cemente 
und verschiedener Mortel Ausdenselben. 

134. i88g, p. 43. — Ueber den Kinfluss des Frostes auf die 
Festigkeit der Cement. 



List of Periodical Literature. 105 

135. BUSCH, A. — Mittheilungen ausder Cement-Teclinik. 
Dinglers Polytechnisches Journ7il^ Vol. 282, p. 116. 

136. DkIvBruck-vStkttin. — Methoden der Untersuchung 
des Cements. Z.des Vereins Deutschen Ing., 188^, 

137. Devai,. — Heifswasser Priifungen fiir Cemente. 
ThonindMslrie Zeitung, Vol. i^, p. 384. (vSee paper 
107.) 

138. Dyckkrhoff, R. — Wirkung der Magnesia in ge- 
brannten Cement. Thofi. Zeit., Vol. 14^ p. 452. 

139. Dyckkrhoff, R. — Ueber die Verfalschung von Ce- 
ment. Difig. Poly. Jour., Vol. 248, p. 24^. 

140. Brdmknger. — Koclien von Cementproben mit 
Hoclidruckdampf. Thonmdustrie Zeit., Vol. 13, p. 

65- 

141. EivBKRS. — Verwertung von Hochofenschlacken. 
Zeitschrift des Verems D. Ing., 188^^ p. 1022. 

142. Fresenius. — Portland-Cement und Nachweis frem- 
der Zusatze zu demselben. Thon. Zeit., Vol. g, p, 71. 

143. Fresenius. — Untersuchung iiber den Nachweis von 
Verfalschungen im Portland-Cement. Thon. Zeit., 
Vol. 8, p. 231. 

144. Gary, M. — Abnulzbarkeit von Cement und Cement- 
mortelu. Tho7ii7idustrie Zeitu7ig, Vol. 75, p. 233. 

145. Grauer. — Wirkung der Magnesia in Portland- 
Cement. Thoti. Zeit., Vol. 15, p. 6^g. Abstract in 
Dinglers, Vol. 282, p. 120. 

146. KOSMAN. — Ueber die Binding der Kalkerde in Hoch- 
ofenschlacken und Portlandcement. Dinglers Poly- 
technisches Jour., Vol. 271, p. 138. 

147. Knapp. — Hochofenschlacke und Portlandcement. 
Dingier' s Poly. Jour., Vol. 26^, p. 184. 

148. Manske. — Cement und dessen Verfalschung. Z, 
des Vereins D. Ing., 1885, p. 921. 

1 49. PhieIvIpp and Beeeeubsky. — Technische Bedmgun- 
gen aus die annahme von Portland zementen bei 
Arbeiten in Ressort des russischen Ministeriums der 
Wegekommunikationen. Civilingenieur, i8g2, p. 

569- 

150. PiNKENBURG. — Schlackencement. Thon. Zeit., 
Vol. 14, p. 768. 



io6 Hydraulic Cement. 



151. SCHUI.ATSCHKNKO. — Notneiiclatur der Luft und 
Wasser-Mortel. Civilingenieur^ 1886, p. ^61. 

152. Takayama, J. Ueber den Gebraucli des zersetzen 
Granitsandes als natiiralichen Mortel in Japan. Di7i- 
glers Poly. Jour., Vol. 2j8, p. 2y^. 

153. Tktmajor. — Lufttreibende Portland-Cement und die 
Darrprobe. Pamphlet, Zurich. 

154. Tktmajor. — Schlackencement. Thon. Zeit., Vol. 
10, p. 177. 

155. TeTmajor. — Ueber die Volumenbestandigkeit hy- 
draulischer Bindemittel. Thon. Zeit., Vol. 11, p. 

U3' 

156. Tktmajor. — Bericht der Subcommission No. 12 der 
zweiten Standigen Commission ziir Vereinbarung 
einheitlicher Priifungsmethoden fur Ban und Con- 
structions-Materialen. Pamphlet, Zurich, i88g. 

157. Wkbkr, C. O. — Praktische Verwendung von Mag- 
nesia-Cement. (See paper No. 73.) Thon. Zeit., 
Vol. 15, p. 341. 

158. ZsiGMONDY. — Ueber die Untersuchurg und das Ver- 
halten von Cement. Dinglers Jour. , Vol. 273, p. 331. 

159. ZsiGMONDY. — Ueber Hochofenschlacken und deren 
Verwerthung. Dinglers Poly. Jour., Vol. 284, p. 233. 

160. ZsiGMONDY. — Ueber den Werth von Heisswasser- 
probenbei derPriifungvon Cement und hydraulischen 
Kalk. Dinglers Poly. Jour., Vol. 280, p. 182. 

161. ZsiGMONDY. — Ueber die Untersuchung und das Ver- 
halten von Cement. Dinglers Journal, Vol. 281, p. 
114.. 

various NOTES, REPORTS AND REVIEWS. 

162. Bestimmung des Oesterreichischen Ingenieur und 
Architekten- Vereins, die einheitliche Priifung und 
Lieferung von Portland-Zement betreffend. Civil- 
ingenieur, Vol. 36, p. 133. Abstract Dinglers, Vol. 
281, p. go. 

163. Ueber die Herstellung und Untersuchung von Ce- 
ment. Dinglers Poly. Jour., Vol. 261, p. 344 a?id p. 

529- 

164. Zur Kentuiss des Cements. Dinglers Poly. Jour., 
Vol. 233, p. 222, and p. 387. 



Topical References to Papers. 107 

VERHANDIvUNGEN DEvS VEREINS DEUTSCHEN 
ZEMENTFABRIKANTEN. 



165. 


Zeit. des Vereins D. 


Ing. 


, 1886, p. 832 a7idp. 854. 


t66. 






1887, p. yjS. 


167. 






1888, p. 7 JO. 


168. 






i8go, p. 7J5J and p. ij8j 


169. 






i8gi,p. 374. 


170. 






i8g2, p. 1054. 



ART. 32. TOPICAIv REFERENCES TO PAPERS. 

In the list of literature in Art. 31, only the titles 
of the papers are given. As nearly all the papers 
mentioned are of value in a general study of the 
subject of cements, and the list is not large, it is 
thought unnecessary to add any explanation or 
comment. 

In order, however, to aid in classifying the ref- 
erences, a topical index is here appended, indi- 
cating, for each of a few prominent headings, the 
papers in w^hich the subject mentioned is most 
fully discussed. 

The papers in x\rt. 31 are numbered consecu- 
tively, and are here referred to by number : 

TOPICAE INDEX. 

Manufacture of Portland Cement. Papers, 4, 12, 20, 24, 
48, 58, 59, 65, 90, 91, 93, loi, 112, 151, 163. 

Manufacture of Natural Cement. Papers, 11, 20, 27, 50, 
55, 58, 118, 151. 

Chemical Theory. Composition. Papers 5, it, 12, 16, 

17, 18, 37, 38. 42, 43, 49, 65, 67, 73, 79, 91, TOO, TOT, 
102, TO4, 108, 109, no, 112, 114, IT5, IT9, 120, T22, 

123, 130, 135, T37, 138, 141, 143, 145, 1^6, 147, T51, 

161, 164. 



io8 Hydraulic Cement. 

Adulteration of Cement. Papers 77, 112, 130. 132, 139, 

142, 143, 146, 147, 148, 151, 161. 

Manufacture of Slag Cement. Papers 20, 28, 60, 89, 114, 
116, .117, 123, 14T, 146, 147, 151, 154, 159, 163. 

Properties of Portland Cement. Papers 16, 31, 35, 38, 
43, 44, 49, 79, 84, 91, loi, 102, 103, 104, 105, 109, 112, 
115, 119, 122, 128, 137, 143, 145, 146, 147, 156, 163, 164. 

Properties of Natural Cement. Papers 11, 33, 35, 38, 43, 
50, 55, 73, 79, 84, 105, 109, 115, 118, 137, 156, 164. 

Properties of Slag Cement. Papers 28, 38, 43, 60, 79, 84, 
114, 116, 123, 132, 135, 146, 147, 154, 163. 

Soundness. Permanence of Volume. Papers 17, 21, 23, 

24, 29, 38, 43, 49, 67, 69, 73, 79, 80, 85, 86, 94, 96, 98, 
100, 102, 104, 106, 107, 108, 109, no, 112, 113, 116, 

119, 131, 135, 136, 137, 140, i43> 145, 153, 155, 156, 
160, 161, 167, 168. 
Methods of Testing. Papers, 8, 14, 15, 17, 18, 21, 23, 24, 
29, 31, 38, 39, 42, 43, 45, 54, 61, 62, 63, 68, 69, 71, 85, 
94, 96, 100, loi, 104, 107, 112, 119, 121, 131, 128, 136, 

143, 148, 149, 153, 156, 161, 162, 163, 164, 165. 
Microscopic Examination. Papers, 8, 37, 112, 120. 
Heat Tests. Papers, 17, 23, 24, 29, 38, 43, 69, 85, 107, no, 

131, 137, 140, 153, 156, 160, 161. 
Use in Mortar and Concrete. Papers. 2, 3, 6, 7, 9, 13, 14, 

25, 32, 33, 34, 35, 36, 40, 41, 42, 46, 47, 49, 5i, 52, 53, 
61, 64, 66, 72, 76, 79, 80, 82, 83, 88, 97, 99, 100, 105, 106, 
108, 113, 129, 135, 158, 164, 169. 

Effect of Sea Water. Papers, i, 14, 25, 29, 38, 47, 49, ^']^ 
79, 80, 82, 86, 100, 102, 105, 106, 109, no, 113, 115, 119, 

13I' 135, 138. 
Permeability of Mortar. Papers, i, 19, 26, 33, 49, 76, 79, 

100, III, 113, t6i, 168. 
Effect of Freezing. — Use of Salt. Papers, 9, 10, 42, 53a, 

57, 76, 78, 132, 134, 158, 163, 167. 
Retempering Mortar. Papers, 14, 32, 75, 100. 



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